Well, suspecting you've put that bounty not on a question of your own (you can always put comments at posts regarding your own questions and answers), seems you've reached catch 22 now.
It's not a bug, the features are addressing orthogonal issues.
- You give away rep for a bounty (probably unwisely)
- You need certain rep to comment on posts that don't involve you
If that question didn't get an answer that satisfies you, and you really didn't find an answer for your concerns, the proper action might have been writing your own question (mentioning your research and all that), rather than putting a bounty.
Alternative solution (plain straight forward), comment before putting the bounty.