How picky are you when it comes to grammar

I saw a post on here about a comment that was criticizing an author's grammar and I wanted to know how picky you guys are with simple mistakes like infrequently or frequently misused commas and stuff like that. Me personally if the writing is consistently bad and the spelling or grammar is absolutely terrible (*cough-wattpad-cough*) I won't keep reading. Sometimes I'll rewrite a sentence that doesn't sound right to me in my head but wouldn't comment abt it if the author didn't ask for constructive criticism. My grammar personally is absolutely terrible so it's not my place to criticize anyway but was wondering yalls opinions on mistakes.