Yes, I’m not sure if that is meant to be a placeholder or a substitute for native user links. What it actually does is generate markup that converts the username into a web link, which is fine for most circumstances, but not ideal. A plaintext username should automatically link to the user. This creates an inconsistent behavior between posts depending on where (and when) they were typed.
In other words, it’s a very helpful feature, but it is not recognizing and linking usernames.