A note on locking: Locking prevents edits and comments on an individual post. The reason for locking a post is nearly always spam edits/comments. Locks are finite in time. Questions that rank highly for popular search queries receive a lot of traffic, and locking is often necessary to prevent vandalism.
On question closure, this is rarely done by moderators (users with a diamond ♦ after their name), but by 5 votes from regular users. Only moderators can lock posts.
I'm curious about the five vote threshold. Has it been fixed throughout the history of the site? Is it still appropriate given the degree to which the site's popularity and traffic has grown?
To be honest, I don't participate in SO that much. The problems with close votes, and the HN community's dislike of the situation is well known. There is no easy fix for the situation, although I do agree something should be done.
The core of the issue, as was pointed out above, is the vtc-please culture in certain chat rooms. Culture is a very hard thing to change (impossible?), and whatever change you make to how closing works is unlikely to be effective unless cultural change is brought about too.
Simple because the fix consists of watching patterns of behavior for a while, identifying the cliques of users who do this, and then mass-banning them, or at least mass-revoking their privileges to close stuff. For maximum cruelty, just reset and peg their reputation permanently at zero.
Not easy because then they're going to scream their entitled little heads off about it, and you'll need to recruit another generation of active moderators.
On question closure, this is rarely done by moderators (users with a diamond ♦ after their name), but by 5 votes from regular users. Only moderators can lock posts.
Disclosure: I am a Stack Exchange moderator