Help for MARK:

MARK allows operators to attach a note to an account.
For example, an operator could mark the account of a
spammer so that others know the user has previously
been warned.

MARK information will be displayed in INFO output.

Syntax: MARK <account> ON|OFF <reason>

Examples:
    /msg &nick& MARK game_boy ON Persistent spammer
    /msg &nick& MARK nenolod OFF