OUT OF CHARACTER WHATEVER
♋ BACKTAGGING: Don't care. Go back as far as you want. If I don't respond chances are my life is eating me alive or I flat-out forgot it was my turn. Nudge me gently and I'll go to it.
♋ BACKLOGGING: I love this stuff. Don't feel restrained to any one timeframe if you want to log anything. Just ask me. I'll most likely say "Yes" or "If you write first I'm game, but I won't respond today because there's no way in hell I'm accomplishing anything today."
♋ FOURTHWALLING: Karkat is aware of the powers of the fourth wall and its inherent ability to make denizens of the universe and alternate universes not give a shit. Similarly, he does not give a shit about fourthwalling. Good luck getting him to believe you.
♋ TRIGGERTOUCHING: I have no triggers, which isn't to say Karkat doesn't. Have at whatever shitty things you can think to heave at him.
♋ OFFENSE: I don't take offense to being told not to do things. If you are annoyed by something I'm doing, let me know. If you have issues, let me know. If you want me to back off, let me know. I put that responsibility on everyone else by automatically assuming no one has a problem with me unless told otherwise. I refuse to cater to players who won't tell me when something bothers them.
IN CHARACTER WHATEVER
♋ TOUCHING WITHOUT CONSENT: Your character will probably get shoved, hit, or screamed at. Unless he knows them -- in which case, your character may get shoved, hit, and screamed at or he'll accept it while being awkward in the way of people who have no idea how to express themselves.
♋ TOUCHING WITHOUT CONSENT WITH SOMETHING OTHER THAN HANDS: Doing this may be subject to removal of said object.
♋ OKAY, CLARIFY THE ABOVE YOU FREAK: Yeah, yeah. Pretty much do anything. Just don't be creepy. He's like
♋ THE ISSUE OF ORIENTATION: Karkat fails to understand how this is even a thing.
♋ RELATIONSHIP PROSPECTS: If you're like Eridan, desperately trying to fill your quadrants and brazenly soliciting anyone who happens to walk in front of you, you can try to woo Karkat. In fact, feel free to awkwardly like him. Just don't expect anything.
Note on the above: given that trolls and teenagers alike pretty much have no idea what the hell is going on with their own feelings and their affections are so volatile, it's possible Karkat may or may not develop a ridiculous crush on your character despite having a current interest in someone else.
♋ HURTING THIS CHARACTER: He's been known to take stabs as a way of saying "Hello, how are you this fine evening." The most you'll get out of hurting him is him freaking out about his blood even though it's been well-established in both canon and TF that it's an issue anymore.
♋ KILLING THIS ASSHOLE: Games generally don't like the senseless killing of characters, so I think it's silly of people to do without asking. Either way, I'm not against it, it's just killing is dumb unless there's a plot reason. We can talk about a plausible way to make him die if you're that gung-ho about it, but I'll probably say no just based on not wanting to make the rest of the cast deal with it.
♋ FOR THOSE WHO READ MINDS: Karkat's brain is a cluster of self-loathing and self-hatred, which he takes out on everyone around him. Those who nudge their way in would have a hard time getting past it to find anything substantial. At most they may discover being in there is like walking on eggshells or glass -- only the eggshells and glass are up-turned razor blades and everything is terrible. If Karkat has involvement in it even slightly, chances are he will make up reasons to blame himself for a problem while simultaneously denying his involvement in it. In short: he's a huge contradiction.