Kyousouka
Dyslexia does not, as far as I know, cause bad grammar
per se, and most spelling problems can be caught by your browser's spell checker :]
(Your post is fine, by the way.)
Whether the comic would be boring or not would depend entirely on how well you write it.
Comics based on Gaia's users tend to be pretty sucky, even in the hands of writers with potential, though. This is because most people aren't willing to give you enough creative control over their avatars (both visually and personality-wise), which makes it difficult to craft a good, tight story. Because of this, Gaia avatar/user stories tend to be all over the place and lack cohesion and structure, which is why most of them are bad.
There are different types of dyslexia some just plane spelling or words some of the grammar of words as well, some are ever dyslexic of numbers. I am dyslexic of words and numbers but i mostly struggle with spelling, grammar as I read better backwards, I did a few tests for it a few years ago but while i have been only I have gotten allot better ^^
And thank you for the advice I have been thinking about making one for a long time but as you say people will not give you the freedom as you need for a story witch would be the big problem...I might make up some gaia's or just use friends that will let me use them as i wish..Or even just do a different story all together then what i was thinking off..
(PS i am using a spell checker for this so yeah XD!]