this question reappeared at the top of the top questions with the notification "community - 1 hour ago". But when I go to have a look at it I can't see any new answers, nor edits in question nor answers. What happened here?
There is a "community user" that goes around and bumps stuff to the front page that it thinks needs more attention. This question has only 1 answer with 0 up votes so it is considered unanswered.
Learn more about this user here: https://electronics.stackexchange.com/users/-1/community
Also take note of their flag weight. The bot flags posts that it thinks needs mod attention and the mods mark valid or invalid just like other users.
There does seem to be an issue with how it is determined for questions to be brought to the front page.
Most affordable FPGA dev kit for learning VHDL and FPGA theory? was just bumped to the front page by community and then was answered by Brian Carlton as a result. Was a question that already had 6 answers, one of which had 6 up-votes on it really needed on the front page again? All that was done was an edit to an answer that Kevin apparently had done incorrectly or something.
How does a PLL inside a FPGA work? was bumped to the front page by community because of a trivial grammar edit performed. I was under the impression that SE's policy was to not perform trivial edits unless needed to make the question understandable.