There's no issue if you are joining and posting different bounty threads as bounty hunters but as mentioned above you will probably be stuck in member rank (if you've purchased copper member rank), if not, you will remain newbie rank which is I think unable to join bounties. You can't contribute very well in the forum if you've focused only on joining bounties and that is the reason for struggling to rank up since there is a merit system introduced as a part of requirements in ranking up.

If I were you read and understand this very well, Unofficial list of (official) Bitcointalk.org rules, guidelines, FAQ and next is this, List of useful Threads!. I'm pretty sure this gives you a lot of information on how to find useful threads. Don't focus on earning bounties, yet you are not breaking the rules but your account look likes toxic member in the forum, did not share any informative nor contributing a good post.