I feel like you and I are kindred spirits. XD
I, too, loathe it most of the time when people use messed up grammar.
However! Being a weird and awkward person with a speech impediment as well, XDXD, I can say objectively you’re right as rain. XD
I am guilty of using improper grammar or slang in text, it just depends on why. I love writing in dialects and trying to write in accents. I bring this up a lot, but in my studying on the Israeli accent and habits, I read this and THEN noticed that they don’t say “Um.” They say “Em.” XD
So if I’m writing dialogue for someone who’s supposed to have that accent, I’ll put “em” in place of “um”. I don’t think there’s anything wrong with that. I feel like sometimes accents can be so deep and make the entirety of English word pronunciations seem different, I won’t do that, like for Scottish accents, DANG! But, to get the point across better, I’ll research phrases they say a lot instead.
However, getting things like
etc. confused, OOF…I can look over it, though and be a little more understanding simply because of my problems with speech. You never know what’s wrong with people, you know? XD