“Care” is probably the wrong word.
“Judge,” perhaps. This is an Internet forum rather than a writing competition sure, but nonetheless if a post appears which contains bad grammar / punctuation / spelling, then one of the following applies to the poster:
1) they’re dyslexic
2) they’re using a clunky client which makes accurate typing difficult
3) English isn’t their first language
3) they’re a cretin
4) they just don’t give a toss
If you fall into the first three then fair enough. If not then your semi-literate scrawling will have an impact on how I (we?) perceive you and how much credence is given to the point you’re trying to make.
Picking people up on typing as a means to winning an argument is lame, though. If that’s the best you can do, you’ve already lost.