The instructions still have the error about showprofile.tmpl. Besides that, the install is just about the same. Same enough to know where things are supposed to go. But, why would you edit showflat.php and not showflat.tmpl? Also, the layout change in showprofile causes the links to look rather junky since it causes a line break. Of course, this is due to resolution and/or side bar(s). When you click "Ignore User" it just refreshes the profile. There is nothing letting you know if it worked or not. The only way to tell is if you browse to a thread where the user posted. If the user is ignored, you will see:
[]You are ignoring this user. See entire thread or unignore this user.[/]
There should be a link on the person's post for ignoring/unignoring. Also, a list of ignored persons could be added to your profile, visible by only you of course.
Bottom-line: It works in 6.3.1. The idea is good, and it's functional, I just feel it could use some more cosmetic/usage tweaking.