If you read further up this particular subthread (which this is a great time to point out would be a lot easier in a threaded format) you will see that we are discussing a comment that is conceptually a reply to two different comments, and @simonlmn is even suggesting not replying directly to either of them.
I actually think that will become a common and annoying trend with Discourse, because it’s what Facebook has trained people to do. Many people will never click “Reply” on a comment; they will instead start a reply at the bottom of the thread with “@username”. To @username this works almost as well, but to everyone else functionality is lost.
PS: maybe some interface could be added so that this kind of mis-reply will be recognized and linked sometimes-correctly?