I see several cases:
- The asker came just to ask one question, got his answer, and moved on. He didn't bother to learn all the features of Stack Exchange like accepting answers. Your comment is just noise because he's never going to read it.
- The asker is new to Stack Exchange, but staying on. Be a little patient, after a few posts he'll wonder what that tick mark is and figure it out. In the meantime, your comment is just noise (it's too early).
- The asker knows how Stack Exchange works. Your answer didn't solve his problem, so he didn't mark your answer as accepted. In this case, nudging for acceptance is downright rude.
So, no, nudging towards acceptance out of the blue is not acceptable in general.
There's one situation in which it is acceptable: if the asker left a “thank you” comment, then it's ok to reply to it and tell him something like
Welcome to Stack Overflow. Please don't leave a comment just to say “thank you”. If this answer solved your problem mark this answer as accepted.”
(You can add something about voting up if the asker already has the required 15 rep.)