I have a few pet peeves when it comes to grammatical errors, too. I am with you on semi-colons also. We should call them the "endangered punctuation" like you said!
Things I hate to see are: their-they're, your-you're, where-wear, and people that misuse words like: he don't, she don't, I axed.
I read that Cambridge, one of the pocket size dictionary people, said they may just start adding words that people use, showing them to be correct, too. No way!! They've got to be kidding!
Trish