Looking at the history: the question was posted in Oct 2010, and got 14 answers in its next 5 days, the last of which was Thurston's. A year and a bit later, on

Looking at the history: the question was posted in Oct 2010, and got 14 answers in its next 5 days, the last of which was Thurston's. A year and a bit later, on Jan 1 2012, two more people posted answers. The question was closed shortly after that, as "no longer relevant". I think you can consider it the opinion of the MathOverflow community that they no longer want to see new answers to the old question and the “already seen” question bumped to the front page again, and closing is a way of doing that (all it does is prevent new answers), and it is not intended as judgment cast on the quality of the question or its answers. I am active in a few Stack Exchange communities (sites), and two things that strike me are: - The communities can differ a lot in how they approach things (when they feel closure is appropriate, for instance). - As in most online communities (Wikipedia etc.), people who have been around for a while tend to get insular and think in terms of their own subculture, and do not always understand what impression their actions (in this example the actual text of the “no longer relevant” closure) make on outsiders or newcomers. On Wikipedia there's an actual policy about this, but I got tired of typing [[WP:BITE]] over and over again. (https://en.wikipedia.org/wiki/Wikipedia:Please_do_not_bite_the_newcomers https://en.wikipedia.org/wiki/Wikipedia:Please_do_not_bite_t...)