My point is that this all comes down to communication, and someone said it already... The point is to be understood.
To a certain extent I disagree, but here's an example of how I disagree.
Someone makes a remark intended to be funny over a text-based medium. If they misspell something, most of the humour is lost in it, because people need to first think about what they meant to say, then add it all up together in their brain, and then "oh". Not funny.
Misppelling leads to an impression of lack of education, or someone being thick (because, much of the time it is! think about the most brainless/immature arguments you've heard, one of the factors you remember is very likely to be poor spelling, and/or use of caps/swearwords etc). Their argument, even if it is an extremely well-communicated (otherwise) argument, and a good/valid one, is likely to be treated differently, because over the Internet there is little to go on to gauge the person's intellect. That can lead to the response being worded differently, possibly condescending, etc.
And if you say "well, it shouldn't lead to that, that's the other person's fault", it's the original poster's fault in the first place for not bothering to spell correctly. We're talking most people here, not people who have real difficulties such as genuine dyslexia.
I think I can get the spelling and grammar correctly, but what I used to do is use a word processor to just check a single word quickly, start it up, type word in, hit spell check. Recently I bought a piece of dictionary software to help me more. Spelling, grammar and punctuation makes a huge difference in an educated/technical discussion.
