@monkeymath
Good post plus funny in places.
We have much common ground on this. I also take care, without going to extremes, to provide a communication that is easily understood by the intended audience. I've no doubt, as well, I miss something here or there.
What we don't know is the actual capability of the writer. Some simply do not write well and an attempt to embarrass or speak down to them to "fix" the situation--when they couldn't even if they tried--doesn't sit well with me.
I don't read a poorly written post and believe that someone's being disrespectful; I assume they're doing their best to communicate. I guess it's possible they are being disrespectful or what have you, but I can't imagine it being more than a minuscule percentage. Say the are being disrespectful or just careless, what kind of response and positive result can be expected toward a pedantic or sarcastic or angry sort of reply? In that case, is the intention really meant to be positive or just mean? I'd say it was mean.
We all have the choice not to read a poorly written post. For those it bothers, I would say skip them. For those who feel compelled to correct in a rude way, I think they enjoy needling and use "bad grammar" as the vehicle for their negativity which can be just a short-term blip or their general personality.
In retrospect, because I don't pay much attention to it, I see posts ranging from "perfect" to "yikes." I'm not bothered by it as I kind of enjoy unwrapping the meaning like a puzzle. Most importantly, I'm not going to attempt to belittle someone by whatever method. If a post is truly indecipherable, there are tons of ways to figure it out by being polite and respectful.