I believe that for twitch channels where the owner has chosen to opt out for globally banned words like 'shit' etc, the messages sent to the irc will automatically replace all instances of this with three '*' signs.
I'm pretty sure that's what OP is looking to trigger on.
I noticed this a couple of days ago when I went into a channel that had this filter on, all messages received through mIRC would appear like this:
[23:19] <inoori> @Nillens the ending was kinda *** up
[00:07] <zestyh> snus aint that bad either, but i dont understand how i started cause i dident really like it, and there were like no pressure for me to start snusing, and it tasted like *** the first 5 times :--- |
While my own messages would appear like "oh shit!" other users would se that as "oh ***"