Well I wouldn't really call it rep-whoring (its a big word), but then asking the OP to accept an answer, when the OP has been a user of Stack Overflow for quite a long time(he obviously would know about accepting an answer), doesn't leave a good impression about you on others.
If the OP is a newbie, or may be has forgotten (you answer has solved the OP's problem, but no answer has been accepted for a long time now), in such a case, you could politely leave a comment to the OP, asking him to accept the answer stating that, this is how Stack Overflow functions. Once the OP has accepted the answer, you may clean up those comments (it would be good to do that, but it's not a mandate).
IMHO, you're being a bit too harsh (rep-whoring) on yourself for asking the OP to accept an answer.