[quote=@Anime_Freak]
<Snipped quote by Halo>

[@Halo] I'm happy that you are taking time to express concern for the misinterpretation of the Japanese language, but as someone who has been speaking Japanese almost their entire life, I have to make some tweaks to your explenation.
We use sempai and senpai together, actually. When we are addressing someone we admire as a tutor or teacher, we use [i]sempai[/i]. This term is used for a senior that you respect normally.
When using [i]senpai[/i], you would use it to address someone that you find as an upperclassmen or senior that you admire with a passion.
Some people interchange them in speech, finding that the person they are addressing fits both descriptions, and that's okay.

Edit: Excuse the mispelled words. I fixed them, but obviously my English needs help xD

[/quote]

Then I've been misinformed by the internet. Curses. :P "Senpai" is indeed the correct romanisation though - I actually wrote a section detailing why "m" was used instead in the traditional Hepburn (something along the lines of what you're saying although I didn't realise the change in pronounciation was deliberate) but deleted it 'cause the post was way too long or something.
And to be honest it wasn't really meant to express concern or turn into a discussion - it was a frivolous comment I thought someone interested in anime/Japanese culture (i.e. the OP) would want to know.