At the behest of the Super User moderators, we've instituted a new question status of protected. A protected question is like a protected Wikipedia article -- it no longer allows additions by anonymous users. Protected questions are indicated in the standard question footer like so:
protected by {moderator name} 3 days ago
This question is protected to prevent "thanks", "me too!", and spam posts from new users. To answer it, you must have more than 10 reputation.
We needed this because some of the more popular Super User questions attracted a lot of noise from random drive-by users who didn't understand how our system works -- users who helpfully provided so-called answers like "thanks, this worked for me!" or "I have this problem too, can anyone help?" And lots of them. Just check out one example of many:
Just be thankful that these deletions you're seeing here are only visible if you have 10k rep on superuser.com. (I should also mention that I captured this full-page browser screenshot using a plug-in recommendation I found on Super User itself.) While we used to lock these kinds of questions, that's not really what a lock was intended for. Locking a question is a bit of a nuclear option in this scenario, as locking prevents the question from getting votes, comments, or edits when the question itself wasn't even the problem. So, in the future, if you see a question that is attracting a lot of drive-by noise answers, please flag it for moderator attention. We'll turn on protection. The protection bar is extraordinarily low right now -- you only need >= 10 reputation to post an answer to a protected question -- but we think this is enough to cut down dramatically on answer noise for certain unlucky, but obviously popular, questions. (and, as always, thanks to our hard working Super User moderators for coming up with this excellent idea)