We've decided it's fine if Agito comes in for the 4th wall on a couple of stipulations. Like you said, so long as A) any thread with both of them features another PC, B) singular tags for replies as you mentioned, and C) we ask that because they share a body in canon that Agito be brought in from the same canon point as Akito is originally from, ie, Agito won't be bringing new canon information "to" Akito, like a canon update.