Its nice to see I have support
But since you asked a question, I will answer it:
1) It's annoying.
2) It's more difficult to understand.
3) It's discouraging, if you don't even put the milliseconds it takes to write two extra characters to improve readability and reduce annoyance, it makes me feel like not putting any effort in answering your questions or responding to your post.
4) It's confusing, especially the way he wrote things down originally (like sometimes using "u" instead of "a").
5) It's better for him* to get used to write things properly, as it can be useful later in life (for example, would you hire something that had "u" instead of "you" in their resume? Or god forbid "4" instead of "for"?)
*-I'm writing "him" and not "you" because I know you are being sarcastic
With all that said, I'd like to thank bgqsl for editing his post.