In my heart, I'm pretty picky about grammar, but on cam I try to disregard that. In some cases, successfully interpreting a really fucked up, one-handed-typing error or ESL mistake is kind of fun - it feels like learning a new language.
It gets irritating when someone, especially someone who is obviously an English speaker, says something that is so poorly phrased that I don't know if it's a question, statement, euphemism, request, or something else. For example: "pussy". Are you asking to see it (especially on a site that doesn't allow that)? Are you asking a question about it, such as whether it's hairy or wet? Are you saying you like pussy? Are you calling me (or one of my visitors) a pussy?
I will say that it tends to increase my moisture levels a bit when a guy demonstrates a solid command of the language. Not so much using big vocab words just for the hell of it or to sound impressive, but if someone casually uses a less-common word in an especially correct manner, it can be pretty hot. The reg that debated (and eventually affirmed) my usage of a semicolon will forever have a special place in my heart.