I used 100 reputation to create a bounty on a question, but this put my reputation at 41. I could not comment in any way on the responses I received because my reputation did not allow me to comment. Either a user should not be allowed to go below 50 when posting a bounty, or the rule should be broken for that post. I know this is a corner case, but it was very frustrating as a user who gave reputation to get an answer, when the answer was more on the right track but still not a complete answer to the problem.
Your feature request makes sense, and it has already been proposed on Meta Stack Exchange: Allow bounty owners to comment on questions they've placed a bounty on, even if they have less than 50 reputation. It has been put on status-review May this year, so perhaps it could be resolved soon.