Doesn't really bother me when it is on a discussion board. Mistakes happen.
So you have heard about the dyslexic devil-worshipper who mistaken summoned 'santa' then?
No, but I did hear about the dyslexic, agnostic, insomniac who spent his nights lying awake wondering whether or not there was a 'dog'.
... on topic now ...
As a moderate dyslexic myself ["Dyslexics of the world untie!"
], I do my best to try to use correct spelling, but I know I make mistakes. I use Google to get a hit on a dictionary entry whenever I get the red squiggly line, and if I cannot find one, I'll substitute a synonym I can spell. My typical error is omitting articles, particularly when I'm typing fast or am tired. So I apologize for any past, present and future misspellings.
I don't mind some of the entries where the sentence structure is not perfect. I've learned a few foreign languages and typically can tell if the post is made by someone where English is their second language as there is a distinct grammatical structure that parallels some of the languages I've encountered. I can make sense of those due to knowing how the foreign language sentence structure works and can understand what the individual was attempting to communicate.
My personal pet peeve are posts written mainly in "text speak". The use of occasional common short cuts, such as "lol" or "rofl" or "imo", I don't mind. It's the ones where the bulk of the post is all in this type of syntax. To me, most of those posts are like deciphering a coded message. Many I am unable to decode so I end up skipping the post altogether.