I have received "polite" requests on 2 questions to accept the posted answer as best by the answerer claiming it will give them a badge. Is it OK, tolerated or objectionable practice?
I've seen some occasions where a user posts a 'thank you, this helped' comment under my answer. If it's a user who is new to the site, and hasn't accepted any answers yet, I usually reply with something like:
Since you're new to the site, I'd like to remind you that you can accept this answer if it helped you. But you can also wait until a better answer comes along.
That's just teaching a new user the basic functionalities of this site, in a way that leaves them with a choice not to accept (yet).
However, seeing that you accept an answer more than half of the times you ask a question, it's rather inappropriate in your case. You can flag those comments as not constructive; comments are meant to request clarification or add minor and transient information. See also this answer by one of the Stack Overflow employees.
P.S. accepting an answer doesn't give them badges (well, most of the times). It's just the +15 reputation that they're probably after.