Star ratings on threads

Hi, after all these years, I just noticed that some threads have stars posted on them.

Who puts those stars there, and what determines if something is "starworthy?"

If this is better in another forum, please move. I just figured I'd get it from the source.

Thanks so much!

It's a standard feature of the vBulletin forum software. Any registered user can rate threads, but few bother to do so. The functionality is relatively popular on a few vB forums but here not so much.