In the end, it's just pure spam and it doesn't contribute anything to the forum, so I should just report it, right?
It does actually to some extent . People join the forum to participates in the bounties, most of them are spammers no doubt but from them you will find some of them become loyal members. I have seen a lot of the examples.
Or is this sort of stuff kinda condoned because it's contained within these bounty threads?
If you feel to report then do it but I think it's better to leave them there because those posts serving a purpose for the bounty participants.