diff --git a/extensions/matrix/src/matrix/monitor/mentions.ts b/extensions/matrix/src/matrix/monitor/mentions.ts
index 70349a0a72a..38a99cfc712 100644
--- a/extensions/matrix/src/matrix/monitor/mentions.ts
+++ b/extensions/matrix/src/matrix/monitor/mentions.ts
@@ -66,25 +66,36 @@ function escapeRegExp(value: string): string {
   return value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
 }
 
-function appendUniqueMentionCandidate(
-  candidates: string[],
-  seen: Set<string>,
-  candidate?: string | null,
-) {
-  const trimmed = candidate?.trim();
-  if (!trimmed) {
-    return;
-  }
-  const normalized = normalizeLowercaseStringOrEmpty(trimmed);
-  if (seen.has(normalized)) {
-    return;
-  }
-  seen.add(normalized);
-  candidates.push(trimmed);
+function resolveMatrixMentionPrefixCandidates(params: {
+  userId?: string | null;
+  displayName?: string | null;
+}): string[] {
+  const candidates: string[] = [];
+  const seen = new Set<string>();
+
+  const append = (candidate?: string | null) => {
+    const trimmed = candidate?.trim();
+    if (!trimmed) {
+      return;
+    }
+    const normalized = normalizeLowercaseStringOrEmpty(trimmed);
+    if (seen.has(normalized)) {
+      return;
+    }
+    seen.add(normalized);
+    candidates.push(trimmed);
+  };
+
+  append(params.userId);
+  const localpart = params.userId ? resolveMatrixUserLocalpart(params.userId) : null;
+  append(localpart ? `@${localpart}` : null);
+  append(params.displayName);
+  append(params.displayName ? `@${params.displayName}` : null);
+
+  return candidates;
 }
 
-function stripNativeMatrixMentionPrefix(text: string, candidate: string): string | null {
-  const pattern = new RegExp(`^\\s*${escapeRegExp(candidate)}(?:\\s*[:,])?(?:\\s+|$)`, "i");
+function stripMatchedMatrixMentionPrefix(text: string, pattern: RegExp): string | null {
   const match = text.match(pattern);
   if (!match) {
     return null;
@@ -92,14 +103,15 @@ function stripNativeMatrixMentionPrefix(text: string, candidate: string): string
   return text.slice(match[0].length).trimStart();
 }
 
+function stripNativeMatrixMentionPrefix(text: string, candidate: string): string | null {
+  const pattern = new RegExp(`^\\s*${escapeRegExp(candidate)}(?:\\s*[:,])?(?:\\s+|$)`, "i");
+  return stripMatchedMatrixMentionPrefix(text, pattern);
+}
+
 function stripRegexMatrixMentionPrefix(text: string, pattern: RegExp): string | null {
   const flags = pattern.flags.replace(/[gy]/g, "");
   const anchored = new RegExp(`^\\s*(?:${pattern.source})(?:\\s*[:,])?(?:\\s+|$)`, flags);
-  const match = text.match(anchored);
-  if (!match) {
-    return null;
-  }
-  return text.slice(match[0].length).trimStart();
+  return stripMatchedMatrixMentionPrefix(text, anchored);
 }
 
 export function stripMatrixMentionPrefix(params: {
@@ -113,19 +125,7 @@ export function stripMatrixMentionPrefix(params: {
     return text;
   }
 
-  const candidates: string[] = [];
-  const seen = new Set<string>();
-  appendUniqueMentionCandidate(candidates, seen, params.userId);
-  const localpart = params.userId ? resolveMatrixUserLocalpart(params.userId) : null;
-  appendUniqueMentionCandidate(candidates, seen, localpart ? `@${localpart}` : null);
-  appendUniqueMentionCandidate(candidates, seen, params.displayName);
-  appendUniqueMentionCandidate(
-    candidates,
-    seen,
-    params.displayName ? `@${params.displayName}` : null,
-  );
-
-  for (const candidate of candidates) {
+  for (const candidate of resolveMatrixMentionPrefixCandidates(params)) {
     const stripped = stripNativeMatrixMentionPrefix(text, candidate);
     if (stripped !== null) {
       return stripped;