OUT OF CHARACTERBacktagging All for it.
Threadjacking/threadhopping If it makes sense to do it IC-ly, and everyone doesn't mind, feel free to.
Fourthwalling Depends on situation, ask first.
ACTIONFighting Zexion prefers to not get into any actual physical fighting, or metaphysical ones for that matter, he's more apt to use people to deal with his fights, than he is to actually get involved in them himself. However, if he's dragged into a fight or is attacked, he is very capable of fighting back using various elemental magic, his blue mage like mimic abilities and illusion. Usually however, unless there's actual reason to stick around and fight, he'll use illusion to attempt to avoid the fight.
Injuries Surface injuries, go ahead, anything beyond easily healed cuts or bruises, like broken bones and such, ask first.
Killing No. Unless it is for a good plot-related reason, and then you'll need to ask/explain why it should be done.
Telepathy/mind-reading Possible, but not easy. Ask first.
RELATIONSHugging Sure, go ahead. Likely will gain you a strange look or an eye-roll depending on who you are.
Flirting Feel free, just don't expect much in return, since he'll likely either ignore it, roll his eyes or leave the area if you don't cut it out after the first ignored bit of flirting.
Kissing and/or other intimate actions Feel free to try, but likely he'll not react in a positive manner if you take him via surprise. Beware the thick-ass book he can summon at will. He's not afraid to use it in a physical manner against people who tick him off or annoy him.
Anything else you'd like to make known? Check out the man's other Permissions involving his illusion and blue mage like abilities, the entry for that is
Here.