I absolutely agree. It's one thing if you post here in the feedback/review section, or make it clear to readers you're interested in constructive criticism, but I have no interest in listening to someone who appears out of nowhere, who I don't know, giving me their opinion on my work. Things like stood up vs stood is ridiculously nitpicky and the sign of someone not to be listened to imo. Writing is about flow and style, so for me, as long as it's readable and preferably easy to read, most rules can be broken (although I always recommend beginners don't, of course, you need to learn them before ignoring them). Like, I don't remember the author's name, but I remember there's a one of those classic novelists that everyone says is one of the greatest, and he just doesn't use grammar, but it works because his writing is that strong. I dislike the way some of my favourite traditional authors format their books (speech in the middle and end of big paragraphs is the most common) but it works within the book and got through professional editing. So, generally, I think any time I see someone giving advice that I haven't even hinted I'm interested in, their profile pic and name go on my mental ignore list.
Not quite grammar but related, I am British, so of course use British-English spelling. Do you have any idea how many times people have tried to "correct" me on my spellings of certain words out of nowhere? Like thanks for your unwanted input but that's a common and accepted spelling and you're showing your ignorance so I'm going to ignore you now.