From what I've seen, the more lenient servers are

irc.daxnet.no [also allows most tor in]
irc.he.net [proxyscanner is a joke]
irc.nac.net
irc.vel.net

Why are some of them not global?

Some servers allow names like NickServ/ChanServ, which results in stolen passwords eventually.

Most others just jupe the nick.