We do that in Malay too :) It´s not only to give our words cutesy effect, but it´s something we do to reflect our seriousness or the lack of it. Most of the misspelled words ended up being further shortened and then used as sms language.

In English, even the grammar is made purposefully wrong for a cutesy effect. In Malay, we´re the same.

I don´t know about languages that don´t follow the Roman Alphabet, though I sure as hell don´t know how to misspell Japanese characters in my essays without changing the meaning completely.