The problem with that is you won't be able to see ANY /who replies anymore.
If your after hiding them from a who when you join a channel, this will do that and still enable you to use the /who command normally at other times
- on me:*:join:#:inc -u99 $+(%,who.,$cid,#) | who #
raw 352:*:if $eval($+(%,who.,$cid,$2),2) { halt }
raw 315:*:if $eval($+(%,who.,$cid,$2),2) { unset $+(%,who.,$cid,$2) | halt }