This is the first idea on the list of Common Suggestions under the header forums.
Though this idea is nice, it can also be solved through improvisation:
Namely, check your posts for errors before hitting submit. It's a habit you should get used to. Also, use the spell check of your browser (I use it all the time), as it helps a lot.
This can all be solved by using your own common sence and when you do write longer pieces of text, you can always use a wordpad or notepad to write them, check it for spelling errors and then submit it... so I don't see the need for this to be implemented!
