Coherence, common sense,
"i dont need to be coherant... people who are dont have common sense"
Wow. Just wow.
First of all if you want to make your voice heard, and your potential audience to take notice (especially of the message you are attempting to convey), being coherent is rather vital. A good grammar is also important if you want the message to be understood. Bad grammar tends to lead to posts where the message gets distorted and misunderstood not to mention quite tedious to try to read if the grammar is particularly bad.
As for the unbelievably sweeping statement that people who are coherent have no common sense. Well, apart from it being obviously utterly incorrect pretty much means you just alienated what I'd expect to be vast majority,if not all, of your potential audience here.