I occasionally like to thank a poster for a good selection of new links, or some good info. Is this also frowned upon now?
No, of course not. That's normal courtesy.
There are some users (unfortunately always the same) who spam numerous threads with their useless crap-posts and tittle-tattle, without really contributing, let alone posting something new.
Especially with Kari Sweets thread it was very bad. Hunter27 and other mods have been cleaning up that thread and deleted close to 20 (!) pages of this crap.