Make the fallback title in the additional reply bold.

This way it stands out from the original additional reply.

app/components/close_help_post.py

@@ -167,7 +167,7 @@ async def close_post(
         delim = ";" if ":" in title_prefix else ":"
         title_prefix = title_prefix.strip("[]").lower()
         additional_reply = f"\n{additional_reply}" if additional_reply else ""
-        additional_reply = f"Closed{delim} {title_prefix}.{additional_reply}"
+        additional_reply = f"**Closed{delim} {title_prefix}**.{additional_reply}"
 
     if additional_reply:
         await post.send(additional_reply)