Permissions
YES
Backtagging.
Thread jacking.
Comment spam.
Figure out he's a troll (of the non-Homestuck kind, think of 4chan with a lot more smilies).
Weird text quirks, Homestuck-related or not.
AT YOUR OWN IC RISK
Hugging/Touching (he'll either avoid it or turn it into something creepy).
Fighting (he'll probably run away before the first punch is thrown).
Stalking (he'll stalk you back. Harder.).
ASK OOCLY FIRST
Private post hacking.
Mind reading/Empathy/Telepathy/etc.
Figure out he's an asshole (unless you're from the DRRR cast, please plot it out with me first, since that'd be OOC for him to be caught before time).
NO
"Out" his internet persona (seriously, no, unless it's plotted out OOCly).
WHY?
People are entirely welcome to figure out Izaya is an internet troll, from the first conversation even. But there's a very marked difference between an annoying network troll and the scope of malicious douchebaggery Izaya is known for and proud of. If you want your character to figure out the first? Awesome, go ahead. If you want your character to figure out the second, however, I'd appreciate if you contacted me first, unless you're part from the DRRR cast or had someone from the DRRR cast out him for you. The point of Izaya is that you don't notice how much of an asshole he really is, until you get a close and personal look at what he can do.
Izaya does not interact "in person" with most people. It's fairly easy to build up CR with his "character" in turn, but not with him. Not unless he's interested in someone in particular, and not if he doesn't have something to gain from this. He's been doing this for a very long time, so he's good at it. Taking his internet personas from him is kind of like killing the character in a way. I'm not saying I'm completely opposed to doing it, I'm opposed to having someone do it for me. So if you wanna plot out something about him and his creepy internet persona or outing him or something? Just contact me first so we can plot it out and have fun with it.
STALKING PERMISSION POST: PLEASE REPLY TO THIS POST ASAP.