servers without admins, and players that impersonate others players.

[Infinity]

this is not a list of rules, its something of a basic guidline to server administration. the server host decides what rules their admins should follow

That are the basic rules, and host should follow most of them or could be reported easily, btw they can add some rules, but not to kick the important rules of that guide.

why should the choice of servers to play on be limited to the "famous" ones because one players got an issue with an impostor?

Who said that list of servers should be limited to famous ones? I said that they should put additional information to contact them and not let people that behave bad (in general, impostors and not impostors) to do what they want because there are people that votes f2 to ban him, with admin or with other system, but It should be a minimun of control.

An obvious solution is account system with authentication using password. I think something like that was work in progress?

I like your suggestion :D But some VPN guys would still doing the same with different nicks.
Maybe it coud be possible that anyone who enter for the first time to masterserver, must put their information per IP. or by logging system.

As for the admin problem, I don't think that there should be global admins like Infinity suggested. Hosting a server should feel like creating a place of your own, with your own maprot and level of strictness, and personal control over it. Ensuring that each server provides contact information should be enough.

The level of strictness should have a minimun and follow most important rules at least, but yes, each server would have different points of view, but with the basic rules.

I suggested 2 alternatives:
-Global administration
-Ensure that servers have contact information
And yes, now that you say, I would see better the option 2, it would be easier.