diff --git a/server/public/model/utils.go b/server/public/model/utils.go
index 527828e26c..5ddadedd1d 100644
--- a/server/public/model/utils.go
+++ b/server/public/model/utils.go
@@ -717,8 +717,8 @@ var (
 func ParseHashtags(text string) (string, string) {
 	words := strings.Fields(text)
 
-	hashtagString := ""
-	plainString := ""
+	var hashtagStringSb strings.Builder
+	var plainString strings.Builder
 	for _, word := range words {
 		// trim off surrounding punctuation
 		word = puncStart.ReplaceAllString(word, "")
@@ -728,11 +728,12 @@ func ParseHashtags(text string) (string, string) {
 		word = hashtagStart.ReplaceAllString(word, "#")
 
 		if validHashtag.MatchString(word) {
-			hashtagString += " " + word
+			hashtagStringSb.WriteString(" " + word)
 		} else {
-			plainString += " " + word
+			plainString.WriteString(" " + word)
 		}
 	}
+	hashtagString := hashtagStringSb.String()
 
 	if len(hashtagString) > 1000 {
 		hashtagString = hashtagString[:999]
@@ -744,7 +745,7 @@ func ParseHashtags(text string) (string, string) {
 		}
 	}
 
-	return strings.TrimSpace(hashtagString), strings.TrimSpace(plainString)
+	return strings.TrimSpace(hashtagString), strings.TrimSpace(plainString.String())
 }
 
 func ClearMentionTags(post string) string {
diff --git a/server/public/model/utils_test.go b/server/public/model/utils_test.go
index 9865ce82c1..67ef4bab5f 100644
--- a/server/public/model/utils_test.go
+++ b/server/public/model/utils_test.go
@@ -541,10 +541,58 @@ func TestStringArray_Equal(t *testing.T) {
 }
 
 func TestParseHashtags(t *testing.T) {
-	for input, output := range hashtags {
-		o, _ := ParseHashtags(input)
-		require.Equal(t, o, output, "failed to parse hashtags from input="+input+" expected="+output+" actual="+o)
-	}
+	t.Run("basic hashtag extraction", func(t *testing.T) {
+		for input, output := range hashtags {
+			o, _ := ParseHashtags(input)
+			require.Equal(t, o, output, "failed to parse hashtags from input="+input+" expected="+output+" actual="+o)
+		}
+	})
+
+	t.Run("long hashtag string truncation", func(t *testing.T) {
+		// Test case where hashtag string exceeds 1000 characters with a space to truncate at
+		longHashtags := "#test " + strings.Repeat("#verylonghashtag ", 50)
+		hashtagString, plainString := ParseHashtags(longHashtags)
+		require.NotEmpty(t, hashtagString)
+		require.LessOrEqual(t, len(hashtagString), 1000)
+		require.Empty(t, plainString)
+		// Ensure it truncated at a space
+		require.NotEqual(t, "", hashtagString)
+		require.True(t, hashtagString[len(hashtagString)-1] != ' ')
+	})
+
+	t.Run("long hashtag string truncation without spaces", func(t *testing.T) {
+		// Test case where hashtag string exceeds 1000 characters with no space after position 999
+		// Create a single very long hashtag that will be truncated
+		veryLongHashtag := "#" + strings.Repeat("a", 1010)
+		hashtagString, plainString := ParseHashtags(veryLongHashtag)
+		// Should be empty because no space was found to truncate at
+		require.Equal(t, "", hashtagString)
+		require.Empty(t, plainString)
+	})
+
+	t.Run("plain text extraction", func(t *testing.T) {
+		hashtagString, plainString := ParseHashtags("hello #world this is #test plain text")
+		require.Equal(t, "#world #test", hashtagString)
+		require.Equal(t, "hello this is plain text", plainString)
+	})
+
+	t.Run("only plain text", func(t *testing.T) {
+		hashtagString, plainString := ParseHashtags("no hashtags here")
+		require.Empty(t, hashtagString)
+		require.Equal(t, "no hashtags here", plainString)
+	})
+
+	t.Run("only hashtags", func(t *testing.T) {
+		hashtagString, plainString := ParseHashtags("#one #two #three")
+		require.Equal(t, "#one #two #three", hashtagString)
+		require.Empty(t, plainString)
+	})
+
+	t.Run("empty string", func(t *testing.T) {
+		hashtagString, plainString := ParseHashtags("")
+		require.Empty(t, hashtagString)
+		require.Empty(t, plainString)
+	})
 }
 
 func TestIsValidAlphaNum(t *testing.T) {
diff --git a/server/public/shared/markdown/fenced_code.go b/server/public/shared/markdown/fenced_code.go
index c8caad5561..22f43bfd63 100644
--- a/server/public/shared/markdown/fenced_code.go
+++ b/server/public/shared/markdown/fenced_code.go
@@ -23,11 +23,12 @@ type FencedCode struct {
 	RawCode      []FencedCodeLine
 }
 
-func (b *FencedCode) Code() (result string) {
+func (b *FencedCode) Code() string {
+	var resultSb strings.Builder
 	for _, code := range b.RawCode {
-		result += strings.Repeat(" ", code.Indentation) + b.markdown[code.Range.Position:code.Range.End]
+		resultSb.WriteString(strings.Repeat(" ", code.Indentation) + b.markdown[code.Range.Position:code.Range.End])
 	}
-	return
+	return resultSb.String()
 }
 
 func (b *FencedCode) Info() string {
diff --git a/server/public/shared/markdown/html.go b/server/public/shared/markdown/html.go
index f15bfb664f..fb63c4198e 100644
--- a/server/public/shared/markdown/html.go
+++ b/server/public/shared/markdown/html.go
@@ -27,69 +27,75 @@ func RenderBlockHTML(block Block, referenceDefinitions []*ReferenceDefinition) (
 	return renderBlockHTML(block, referenceDefinitions, false)
 }
 
-func renderBlockHTML(block Block, referenceDefinitions []*ReferenceDefinition, isTightList bool) (result string) {
+func renderBlockHTML(block Block, referenceDefinitions []*ReferenceDefinition, isTightList bool) string {
+	var resultSb strings.Builder
+
 	switch v := block.(type) {
 	case *Document:
 		for _, block := range v.Children {
-			result += RenderBlockHTML(block, referenceDefinitions)
+			resultSb.WriteString(RenderBlockHTML(block, referenceDefinitions))
 		}
 	case *Paragraph:
 		if len(v.Text) == 0 {
-			return
+			return ""
 		}
 		if !isTightList {
-			result += "<p>"
+			resultSb.WriteString("<p>")
 		}
 		for _, inline := range v.ParseInlines(referenceDefinitions) {
-			result += RenderInlineHTML(inline)
+			resultSb.WriteString(RenderInlineHTML(inline))
 		}
 		if !isTightList {
-			result += "</p>"
+			resultSb.WriteString("</p>")
 		}
 	case *List:
 		if v.IsOrdered {
 			if v.OrderedStart != 1 {
-				result += fmt.Sprintf(`<ol start="%v">`, v.OrderedStart)
+				resultSb.WriteString(fmt.Sprintf(`<ol start="%v">`, v.OrderedStart))
 			} else {
-				result += "<ol>"
+				resultSb.WriteString("<ol>")
 			}
 		} else {
-			result += "<ul>"
+			resultSb.WriteString("<ul>")
 		}
 		for _, block := range v.Children {
-			result += renderBlockHTML(block, referenceDefinitions, !v.IsLoose)
+			resultSb.WriteString(renderBlockHTML(block, referenceDefinitions, !v.IsLoose))
 		}
 		if v.IsOrdered {
-			result += "</ol>"
+			resultSb.WriteString("</ol>")
 		} else {
-			result += "</ul>"
+			resultSb.WriteString("</ul>")
 		}
 	case *ListItem:
-		result += "<li>"
+		resultSb.WriteString("<li>")
 		for _, block := range v.Children {
-			result += renderBlockHTML(block, referenceDefinitions, isTightList)
+			resultSb.WriteString(renderBlockHTML(block, referenceDefinitions, isTightList))
 		}
-		result += "</li>"
+		resultSb.WriteString("</li>")
 	case *BlockQuote:
-		result += "<blockquote>"
+		resultSb.WriteString("<blockquote>")
 		for _, block := range v.Children {
-			result += RenderBlockHTML(block, referenceDefinitions)
+			resultSb.WriteString(RenderBlockHTML(block, referenceDefinitions))
 		}
-		result += "</blockquote>"
+		resultSb.WriteString("</blockquote>")
 	case *FencedCode:
 		if info := v.Info(); info != "" {
 			language := strings.Fields(info)[0]
-			result += `<pre><code class="language-` + htmlEscaper.Replace(language) + `">`
+			resultSb.WriteString(`<pre><code class="language-` + htmlEscaper.Replace(language) + `">`)
 		} else {
-			result += "<pre><code>"
+			resultSb.WriteString("<pre><code>")
 		}
-		result += htmlEscaper.Replace(v.Code()) + "</code></pre>"
+		resultSb.WriteString(htmlEscaper.Replace(v.Code()))
+		resultSb.WriteString("</code></pre>")
 	case *IndentedCode:
-		result += "<pre><code>" + htmlEscaper.Replace(v.Code()) + "</code></pre>"
+		resultSb.WriteString("<pre><code>")
+		resultSb.WriteString(htmlEscaper.Replace(v.Code()))
+		resultSb.WriteString("</code></pre>")
 	default:
 		panic(fmt.Sprintf("missing case for type %T", v))
 	}
-	return
+
+	return resultSb.String()
 }
 
 func escapeURL(url string) (result string) {
@@ -137,31 +143,37 @@ func RenderInlineHTML(inline Inline) (result string) {
 		}
 		result += ` />`
 	case *InlineLink:
-		result += `<a href="` + htmlEscaper.Replace(escapeURL(v.Destination())) + `"`
+		var resultSb strings.Builder
+		resultSb.WriteString(`<a href="` + htmlEscaper.Replace(escapeURL(v.Destination())) + `"`)
 		if title := v.Title(); title != "" {
-			result += ` title="` + htmlEscaper.Replace(title) + `"`
+			resultSb.WriteString(` title="` + htmlEscaper.Replace(title) + `"`)
 		}
-		result += `>`
+		resultSb.WriteString(`>`)
 		for _, inline := range v.Children {
-			result += RenderInlineHTML(inline)
+			resultSb.WriteString(RenderInlineHTML(inline))
 		}
-		result += "</a>"
+		resultSb.WriteString("</a>")
+		return resultSb.String()
 	case *ReferenceLink:
-		result += `<a href="` + htmlEscaper.Replace(escapeURL(v.Destination())) + `"`
+		var resultSb strings.Builder
+		resultSb.WriteString(`<a href="` + htmlEscaper.Replace(escapeURL(v.Destination())) + `"`)
 		if title := v.Title(); title != "" {
-			result += ` title="` + htmlEscaper.Replace(title) + `"`
+			resultSb.WriteString(` title="` + htmlEscaper.Replace(title) + `"`)
 		}
-		result += `>`
+		resultSb.WriteString(`>`)
 		for _, inline := range v.Children {
-			result += RenderInlineHTML(inline)
+			resultSb.WriteString(RenderInlineHTML(inline))
 		}
-		result += "</a>"
+		resultSb.WriteString("</a>")
+		return resultSb.String()
 	case *Autolink:
-		result += `<a href="` + htmlEscaper.Replace(escapeURL(v.Destination())) + `">`
+		var resultSb strings.Builder
+		resultSb.WriteString(`<a href="` + htmlEscaper.Replace(escapeURL(v.Destination())) + `">`)
 		for _, inline := range v.Children {
-			result += RenderInlineHTML(inline)
+			resultSb.WriteString(RenderInlineHTML(inline))
 		}
-		result += "</a>"
+		resultSb.WriteString("</a>")
+		return resultSb.String()
 	case *Emoji:
 		escapedName := htmlEscaper.Replace(v.Name)
 		result += fmt.Sprintf(`<span data-emoji-name="%s" data-literal=":%s:" />`, escapedName, escapedName)
@@ -172,25 +184,30 @@ func RenderInlineHTML(inline Inline) (result string) {
 	return
 }
 
-func renderImageAltText(children []Inline) (result string) {
+func renderImageAltText(children []Inline) string {
+	var resultSb strings.Builder
 	for _, inline := range children {
-		result += renderImageChildAltText(inline)
+		resultSb.WriteString(renderImageChildAltText(inline))
 	}
-	return
+	return resultSb.String()
 }
 
-func renderImageChildAltText(inline Inline) (result string) {
+func renderImageChildAltText(inline Inline) string {
 	switch v := inline.(type) {
 	case *Text:
 		return v.Text
 	case *InlineImage:
+		var resultSb strings.Builder
 		for _, inline := range v.Children {
-			result += renderImageChildAltText(inline)
+			resultSb.WriteString(renderImageChildAltText(inline))
 		}
+		return resultSb.String()
 	case *InlineLink:
+		var resultSb strings.Builder
 		for _, inline := range v.Children {
-			result += renderImageChildAltText(inline)
+			resultSb.WriteString(renderImageChildAltText(inline))
 		}
+		return resultSb.String()
 	}
-	return
+	return ""
 }
diff --git a/server/public/shared/markdown/indented_code.go b/server/public/shared/markdown/indented_code.go
index a89ee6c70c..9a4a6b8212 100644
--- a/server/public/shared/markdown/indented_code.go
+++ b/server/public/shared/markdown/indented_code.go
@@ -19,11 +19,12 @@ type IndentedCode struct {
 	RawCode []IndentedCodeLine
 }
 
-func (b *IndentedCode) Code() (result string) {
+func (b *IndentedCode) Code() string {
+	var resultSb strings.Builder
 	for _, code := range b.RawCode {
-		result += strings.Repeat(" ", code.Indentation) + b.markdown[code.Range.Position:code.Range.End]
+		resultSb.WriteString(strings.Repeat(" ", code.Indentation) + b.markdown[code.Range.Position:code.Range.End])
 	}
-	return
+	return resultSb.String()
 }
 
 func (b *IndentedCode) Continuation(indentation int, r Range) *continuation {
diff --git a/server/public/shared/markdown/reference_definition.go b/server/public/shared/markdown/reference_definition.go
index 69e8ed9401..1c40cf83a1 100644
--- a/server/public/shared/markdown/reference_definition.go
+++ b/server/public/shared/markdown/reference_definition.go
@@ -3,6 +3,8 @@
 
 package markdown
 
+import "strings"
+
 type ReferenceDefinition struct {
 	RawDestination Range
 
@@ -24,10 +26,11 @@ func (d *ReferenceDefinition) Title() string {
 }
 
 func parseReferenceDefinition(markdown string, ranges []Range) (*ReferenceDefinition, []Range) {
-	raw := ""
+	var rawSb strings.Builder
 	for _, r := range ranges {
-		raw += markdown[r.Position:r.End]
+		rawSb.WriteString(markdown[r.Position:r.End])
 	}
+	raw := rawSb.String()
 
 	label, next, ok := parseLinkLabel(raw, 0)
 	if !ok {