The policies that are in place here are remarkably few in number. The only hard and fast rule here (beyond the usual stuff about illegal activities and such) is no personal attacks. Beyond that, we have very liberal policies in place about what is allowed here and what isn't. Just having the right to delete one's own messages is extremely rare on many forums, but we give people that option here.
The governing of this community specifically has been mostly through experience. In the majority of cases, a one time incident doesn't mean we need a new rule to cover it. I am quite conservative about implementing new rules or regulations here. But when something happens repeatedly and it becomes a problem, just like steering a ship, a course correction may become needed.
BetterMost residents retain the right to have their accounts deleted, but I have added a cooling-off policy by requiring an administrator process the request. We have had repeated instances of people using that option as a dramatic tool to engage in needless theatrics on their way out the door (last summer in particular), followed rapidly by applications for new accounts from these same people to lurk and watch for any reaction they may have gotten. I've also had several occasions where people have asked for account deletions only to change their mind a week later, reapply for a new account, and then try and carry on threads under a new handle, having to remind people they have a different handle now. All of this would have been unnecessary had they just given a week or two to consider whether their decision was "heat of the moment," and in the vast majority of cases, what was causing the problem for them then had been resolved, blown over, or just wasn't as important any longer. You aren't required to use your account either, and in some cases, a vacation from the online world isn't a bad idea.
Once a user's account is cancelled, their identifying information (IP address and such) goes with it, so it makes it much more difficult to track stealth accounts unless I start keeping records on deleted accounts, and that really doesn't interest me.
When a resident asks to delete their account, it is common for one of us to ask why, but only because we do care about our community here and want to know if we can help in some way. But a reason or explanation isn't a requirement. We just ask the person to confirm their request after a 14 day waiting period.
This policy has worked extremely well for us, and I think the fact we reach out to our community here when something does go wrong makes us unique and special.