Some postes are randomly green to me...

[Ashtoreth]

That means the OP has marked it as the answer to the thread. If you post a help thread in the technical support section, you get that option. It's not.. always accurate though. Some people just pick a random post.

Yeah, the problem with this feature is that any Guest/Unregistered User can mark a post as "best answer" even if they're not the thread creator, as long as the OP is a Guest/Unregistered User too.

I tested this myself with a thread in which the post where the issue was being reported was marked by someone as "best answer" (who the hell does that?). I was able to unmark it without being logged in.