As long as the post itself is on-topic and understandable, grammer should matter much:
I do want to hear the thoughts of people who can't speak perfect English
Shouldn't**
Mods, delete this guy's post, such poor grammar
(j/k of course) OP, the thing is that in 99% of the cases, posts with poor grammar are also insubstantial.
Of course there isn't a real way to measure this, but it has just been my personal experience.
If your friend wrote posts that consisted of just 1 or 2 sentences, while also containing poorly grammar, mods are justified in removing those.
I suspect this was the case, but do add some examples if you have any.