@MartinSleziak Henno Brandsma was well-known as a font of topological knowledge. This is a tragic loss for our community as well.

This is of course a good answer, but Re the last sentence of the first paragraph: it's not suitable even if they did barge in and pushed a copy, etc. :-) At least not before they had established credibility. An incredibly ingenious 3-page technique that had somehow been overlooked by everyone ought to be able to handle other hard problems with impressive dispatch, and this is what every amateur would-be Solver of Big Problems ought to cultivate. Such amateurs could even pose challenges in the manner of 16th century mathematicians, just to demonstrate how bloody ingenious they are.

In answer to the first question: not quite like a jury, since the voters don't get together to deliberate. People vote as individuals. But yes, other people who think a closed question has merit can vote to reopen it.

@alephzero Would "compelling and good-faith reason" satisfy you? Of course cheating is an occasional problem, but the majority of attempts (from e.g. undergraduates) are summarily shut down. Cases of cheating that sometimes get further include contest problems. But this community is pretty alert.

@მამუკაჯიბლაძე I can raise this question with my fellow moderators.

@FedericoPoloni Yes, indeed, that has happened. But I can't recall a case where someone both assembled a bunch of comments into an answer and flagged to have comments removed.