It's truth. "I'm" is universally capitalized because "I" is the first-person pronoun and "I'm" is a contraction of "I" and "am".
I err, guess I don't type/write about myself in the first person often enough. To think they let me do A-level English Language. I assumed that we'd dropped the capitalisation 'cos 'i'm' has been around a long time, and that the yankees only still do it because they're stuck with dictionaries from 1773.
What the hell are they teaching you?... Anyway, I don't mind, I'd rather capitalise the I in I'm as it is I am, it just makes sense to me. Also, I'm glad we're not having a fist fight over this... Please don't start.