Sorry op I think it's sneery and unnecessary too.
Sen, including dyslexia, physical disabilities including sight loss (speech to type software can be appalling for using the wrong word), esol speakers especially those who HAVEN'T been taught English formally but are self taught, all very good explanations for why the writers English may be less than perfect.
In addition some of the 'errors' mentioned aren't considered errors but dialectal difference. And in informal settings - such as a chat board, people tend to type as they speak.
I've an English degree linguistic and dialectal history modules were included. All languages are fluid and perpetually evolving, we no longer write/speak like Chaucer or even Shakespeare, or Austen or Dickens.
Italians no longer speak in pure Latin (just ask Dante Alighieri).
Word and phrase meanings, spelling and usage change.
We see it most with teenage subversive usage - 'sick' 'bad' but also with the creation of new words through eg advertising and the creation of portmanteau words, brand names becoming verbs 'hoover' 'sellotape' ...
I think it's fascinating.