k 0.6.0 Channel has a "key" (a password).
l 0.6.0 Channel has a user limit.
m 0.3.0 Channel is moderated, only "voiced" users can send messages.
+ M 20 Only registered users (and IRC Ops) can send messages.
n 0.3.0 Channel doesn't allow messages of users not being members.
O 18 Only IRC operators are allowed to join this channel.
P 0.5.0 Channel is "persistent".