Not sure, but it would have something to do with Q's reply to the troll:
Troll: WHAT HAPPENED TO 11/11/18 UNIFIED AMERICA DAY YOU DISGUSTING LIAR FRAUD???
Q: Do you believe your efforts here persuade people to stop the pursuit of TRUTH, [CA_J]?
[CA_J] has a contextual relationship with [Do you believe your efforts here persuade people to stop the pursuit of TRUTH,]
"here" [8chan] may also be relevant.
Followed by what seems to me perhaps an invitation to join the movement:
There is a place for everyone.
Q
I agree.. I think Q is actually semi-doxxing someone. Calling them out, but name.
Plus Q does not dispute anon's use of "11/11/18" as a date. He only addresses anon's definition of "unified".
And if that's the case, CA_J may represent something only known to themselves or those in the know. Of course there are other possibilities - CA_J may represent a proof the troll is having no effect.