I've noticed that the system user 'Community' bumps up un-accepted questions quite often. Now, the issue is that most of these questions have satisfactory answers, and the OP may even have indicated as in the comments that the question has been satisfactorily answered (example: How do I find the tension in additional strings in this problem?). The OP just hasn't clicked the accept button (maybe it wasn't obvious to them?)
These questions clutter up the main page and push new questions downwards.
I propose that moderators(or xyz rep users) be allowed to semi-accept an answer that is most probably correct, it just hasn't been accepted by an inactive OP. The semi accept shouldn't have a rep bonus, its only functionality is to stop Community from bumping. Maybe we can have a flag option for semi accept.