I admit to occasionally down-voting nodes because of poor grammar, spelling, or punctuation, especially when it seems that the poster's first language is English¹. Usually, I don't down vote regardless of how egregious the usage problems are, but when the usage errors are severe enough to make the question incomprehensible, I do.

I do reserve the right to completely ignore, down vote, and make snarky comments about nodes where the author has deliberately flouted the rules of literate English as an affectation. Can I determine this reliably? No. Do I try? Yes. Do I care? Well, yes. I'm not going to get all cranky about split infinitives or double negatives or obvious typos, like "teh" for "the," nor do I much care about the confusion of words like affect|effect², who|whom³, or it's|its⁴.

I also have found that trying to explain a problem in clear, grammatical English helps me to its solution⁵. After all, if I can't explain the problem to myself, how can I explain it to somebody else?

1. People for whom English is not their first language tend to make different mistakes than do those for whom English is their first tongue.
2. See Affect vs Effect
3. See who or whom
4. See Some Common Mistakes And How to Avoid Them
5. It also helps me when I'm trying to modify the code because somebody decides to change the requirements.