Mine will split if you mess with them enough too. It's a survival reaction. If they feel threatened, by water parameters, injury, etc... they can/will split.
I was just messing with mine trying to get it to dislodge once and it ended up splitting that night. I didn't tear it or anything, but it still split that night. It was pretty small too, so they don't have to be big to split. Mine seem to split if I feed them too much or mess with them much.
I've had them move around a touch a few corals, and the reaction varies.
My leathers don't seem to care one bit. Either the BTA's don't sting them or they don't care. I've had BTA's nuzzled right up to leathers for long periods of time with no issue.
I've had them touch SPS and the SPS RTN pretty quick. When they've touched my torches, they seem to both sting each other at times and rip each other's tentacles off, but other than that, no death's between those. BTA's will also sting and injure monti's and other encrusting sps. polyps will retract and then algae can start growing on that spot if you let it happen too long.
I'm in the process of trying to catch and get rid of a few splits in my tanks. I've gotten 8 out so far. They are becoming a pain trying to keep them away from my ever growing corals.
If anybody near me wants one, let me know, haha.
