There's a difference between a post written by a native English speaker who doesn't give a crap and a post written by someone for whom English is a foreign language. The latter's mistakes have the flavor of someone who's making an honest effort and just doesn't quite get the rules just yet, or their spelling and grammar pass but their idioms and phrasing are off. Not wrong, but not the way the native speakers put it. If I see a post written by the former, I make certain judgments (it's a very good first-order crud filter). If I see a post written by the latter, I give the writing due attention. Whoever wrote it obviously cares enough to try and express themselves in a secondary language for the benefit of their audience and I gotta respect that. Especially since I have a husband who is not a native English speaker and who has refused to join HoF partially because he sees it as my space and partially because he doesn't want to futz with English in his recreational time. I'd put a post written by someone who's obviously got a point but just can't spell their way out of a wet paper sack in that camp too, though I admit that if the spelling and grammar are too mangled it is not possible for me to tease the point out.
But then there're posts written by people whose command of the English language is just fine, but whose writing style is just awful or whose logic circuits are either disengaged, shorted out, or not even there to start with. Grammatically correct sentences that express ideas that make no sense. Bold claims with absolutely nothing to back them up. Repeated lies, long since debunked, that they cling to because they're just so truthy. Crappy communication and no idea that their communication is crappy, or, worse, a deep-seated belief that it isn't their problem their writing sucks. That's my second-order of filtering and that's where my despair really starts to set in. There are a lot of people who post comments on blogs and news sites who know how to write in English but, if they have even the slightest clue as to how to use their brains effectively, it is NOT coming across in their posts.
ETA: my cursive sucks. It is legendary for its suck. My print is much better. It won't pass for type-set or anything, but it's legible (in fact, I've found that lab rats with crappy handwriting are few and far between, probably because of keeping notebooks). My signature, OTOH, is godawful. Neither my first or last name come out spelled right and in fact it's not clear there're even letters. My sister described it once as "a squiggle and a...what
is that?" When I initialize something, it's not much better. One of my labmates called me on it once, pointing out that none of the letters were recognizable.
I feel the same way and I always feel so . . . snobbish. I mean, spelling isn't everyone's strong suit. But I can't overcome the feeling. I'm glad I'm not alone.
I try to spell well, though, so I'm not a total lost case, I hope. 
