Epochtalk will allow only a restricted set of characters in usernames (the same set as hostnames, IIRC). Alongside every post will be the person's username as well as their far-less-restrictive display name. This should help in a lot of cases.
Trying to detect similar names in general seems pretty difficult. I'm not sure how it'd be done.
It would be difficult to detect different names, but an idea that came to mind would be generating a small image, or a certain color from the hash of someone's username. That way, each color or image should be (at least slightly) different, even when a username is extremely similar. The one problem I could foresee with that approach would be having an ugly color, or small image beside every user's name on all posts and PM's. Trying to detect similar names in general seems pretty difficult. I'm not sure how it'd be done.
