I have been into project to where BM had required signature bounty participants to post in ann threads of the said project. Thus, bumping ann threads will likely to happen. This could never be a fault of a bounty hunter.
In order for this to be prevented in the future since the forum has set users with the forum rules and regulations, so it is about time also to set rules and regulations for the bounty manager. This will help to gain a fair and equal treatment of every project in the forum.
If you didn't know signature campaign can't force or encourage bounty participants in any way to post in the current ann thread. It is prohibited by forum's rules. So, if you find any you can report to moderators.