I apologize for dredging this up again, but if any individual users would like to add ignore functionality to the forums, I think I've found a way to do so.
EDIT: This only works in Chrome. If anyone prefers Firefox, post here (or pm me) and I'll see if I can find out how to do it in Firefox too (it involves Greasemonkey I think). I have no idea if this is even possible in Internet Explorer, but if you're using IE you should probably sit down and re-evaluate your life choices.
1. Go to this page
and scroll down to the second post by Unarmed (the tenth post on the fourth page).
2. Copy and paste the code into a text file and save it as [filename].user.js.
3. Drag the file into Chrome and install it.
4. Whenever you read a thread, users will have little "x" marks next to their usernames. Click the x to toggle ignoring that user's posts.