As I posted on the other thread, I would never pick someone up for bad spelling grammar as that is such bad form, but I can't understand someone 'being completely baffled as to why people would care about spelling mistakes'. You're baffled as to why people want to get something as fundamental as the way we communicate right? Seriously?
Put it this way - I can understand why you would want to roll your eyes at pedants making people feel stupid for their errors. But to be 'baffled' at why people care about accurate spelling/grammar smacks more than a little of hyperbole.
There are certain posters on this very thread whose posts I have to re-read before I can make sense of them, and that makes it too much like hard work me want to switch off from, or gloss over, their posts.
When people use the wrong words which alter the meaning of a sentence, or render it meaningless; yes, you can work out what they're saying from the context, but why should people have to put in that extra work to decipher what you're saying? Again, it makes people switch off. Typos are different - we all make those.
Do other languages have the same issues with poor grammar and spelling? Do Germans use whole other words in place of the correct one ('there' instead of 'they're', 'your' instead of 'you're', whacking in unnecessary possessive apostrophes, for example)? Do they use text speak?
It must be difficult for non-speakers of English to decipher what is being said when incorrect words are used. It's bad enough for English speakers. 