A kill (or collision) and a kick crossing eachother can
cause protocol violations.
On server1, user1 and user1b are (the only ones) in
#foo. user2 is a user on server2.
At the same time (so the 2 events cross eachother)
user1 kicks user1b and user2 kills (or nick collides with)
user1b. Now server2 just ignores the kick it receives
(because the kicker doesn't exist anymore), and thinks
user1 is still on #foo.
If user1 now joins the channel again, server2 sends a
wallop: Protocol Violation from user1: user1 tried to
CREATE a channel already joined.