This question already has an answer here:
It happens quite frequently that the OP hints that he/she accepts the answer but fails to press the check mark button. (For instance, after a relatively long and time consuming discussion the OP's closing comment goes like "Oh, I understand now, thanks a lot." But then nothing happens. I felt always that it would be shameful to say: "Then, please do accept my answer by pressing that nice little check mark on the left." I don't think that I will ever do that. Yet, I am curious to learn what the community's opinion is about such situations.