Sometimes someone may post more than one comment on a post. If I am referring to one of their older comments it is hard to tell which one I am responding to, without going into details in the comment ("Regarding your comment on January 21st, [...]").
It would be nice to add a chat-like reply feature, where your comment's @ mention is replaced with a link to a specific comment, while still appearing as an @ mention, but with a reply symbol in front of it. Clicking on the mention would highlight the replied-to comment.
Here is a screenshot of something similar in chat: