Lots of questions that are put on the frontpage by 'Community' are old questions that have answeres but none are accepted. They've been abandoned by the original asker, and they're useless to build on, but they're perfectly fine to keep. Is there a way of accepting an answer on behalf of the original user so the question will not pop up again?
As far as I'm aware community 'bumps' questions for which there are no answers. The SE definition of no answers is no accepted or upvoted answers.
If as you suggest, they are worth keeping around. then chuck an upvote on a suitable answer (or more than one), then Community will have done it's job and the Q&A will sink into the database.
If the Q&A is of no value, then it can be closed or downvoted and deletd in the usual manner.
Only the OP can accept an answer.