i don't think it's rude, as such. It can be annoying to read through a post with poor grammar (incorrect tenses, was replacing were etc) and next to no punctuation, but the poster isn't trying to be rude, they see what they're typing as acceptable.

I often cba (see what I did there) to type certain things. An example is the lack of capatalisation on the 'i' at the very beginning of this post. I found it easier to just hit the 'i' key.

The 'net has made this kind of thing perfectly acceptable, as long as it's confined to the Internet. Also keyboards are a poor way to input characters, because you are likely to hit another key, or miss the space bar.

What I find more unacceptable is the recalcitrant nature of someone who is unwilling to accept that they have offended someone, and responds with bad language or abuse; 'flaming'.

i'd rther reed a post lik this than have to read through 4 lines of filth.