Glad to see this thread, as I was curious about this for our boys... I will start abit of "mirroring" on occasion to keep everyone active and happy.
Funny thing, the male that's by himself, flared like nobody's business, very impressive. The other male that's in the community tank, didn't flare and actually avoided the mirror! Is it because the bachelor betta has a bubble nest and wants to defend it (although it's empty, just bubbles), and the community betta doesn't? Or are they just different personalities?