agree, just like posts in off topic board don't count in person's post history, same can be done for bounty board, wouldn't take much effort, I guess.
I never really understood the desire to make certain posts not count for "post count". That means the post count is something else than the name suggests.
Are there still bounty campaigns that pay for spamming based on only the post count, without checking anything else? Any campaign manager who does a decent job would just check the post history, and count from there.
If anything, I'd say remove signatures on certain boards, and count all posts. But that'll just move the spam to other boards so it doesn't work either.
There is actually an argument to completely separate the bounty section from the rest of the forum -- posts wouldn't count towards post count, or activity and would be in a separate section of a person's post history. The bounty hunters don't generally appear interested in participating in the rest of the forum, and the rest of the forum generally isn't interested in what bounty hunters do.
I'd argue this same argument could be used as an argument to get rid of altcoin bounties entirely: if it's going to be a completely separate section, why should Bitcointalk be the site to facilitate this? Let any other site deal with it.