What happens in the following situation: I posted some question, soon after one person response in the answer. However the answer was not enough detailed for me: I posted the comment encouraging this person to provide some more details, however he didn't do that. Then I started the bounty for this question. Now I would like to ask, whether this person will receive a message about activity in this topic or should I (at least) post some comment to be sure that this user will at least see my bounty?
Placing a bounty on a question will not directly notify a user that answered it.
I am not convinced it is useful to inform the answerer again that you want a more detailed answer, but it would not be redundant with the bounty and not out-of-line either.