How does a question get "bumped to the homepage"?

Question

A couple times recently (on this question and this question in particular) I've seen a Meta post that was 'modified' by the Community. When I open the question, I don't see any changes, just a notice saying

bumped to the homepage by Community♦ 1 hour ago

This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.

Does anyone know what exactly causes a question to be 'bumped'? My guess is it is somehow related to the number of answers with no votes, comments, or accepts. Does this happen on the main site too, or just on Meta?

Answer 1

The Community user randomly bumps certain old questions -- questions that were good enough (positive score) to attract at least one answer, but no answer is upvoted. On a busy site this can mean that the answer wasn't noticed. Or maybe there's something wrong with it. Or maybe the question needs to be improved. So, it's a question that should get another look -- for voting, editing, additional answers, etc.

The Community user doesn't bump questions with no answers; there has to be at least one answer languishing there. I'm pretty sure that comments don't factor into it.

The Community user has been bumping questions for years, showing on the front page as modified by Community. That's confused a lot of people over the years, so recently SE added the notification banner that you quoted.

Bumping happens on both main and meta. I think it's more frequent on main.