It depends on the context.
gross misspellings i find acceptable:
In heat of battle:
Joebobtaru: thres a cwralr bhnd u! MOVE!
ok guys trying to warn the pt and typing faster than he is physically capable of doing correctly.
Jokingly in party:
Mistaya uses Fast Blade.
Mistaya Misses the Crawler.
Mistaya: OMGWTFBBQ i r teh sux0rs ;_;
(this is mainly with ppl from your LS or other close friends, not gonna do that in a pickup pt/ JP pt.)
If someone types like a 2 yr old talks in normal chat... i dunno i dont have any issues with him but i kinda roll my eyes. Never got a leetspeak pt invite but i would probably not take it because frankly i despise it. (hence why saying 'i r teh sux0rs' in pt would be a highly sarcastic joke)
so yeh situational. Not gonna skewer the man who cant spell, or the guy whose lagged' in jeuno, but at least try to spell like a human being o_o;
EDIT:
c0m3 0n guy5 17'5 n07 7h47 b4d
oh dear i understood that without looking twice ;_; heeeeellllp meeeee