Like are there checks where a quest-giver or trainer or the like will say "I'm sorry but you're just not famous enough" and refuse you service? Or is it just some kind of personal score?

I know reputation affects shop prices, light & dark magic instruction and I want to say whether people will join up with you. Does fame serve as some kind of modifier for your reputation? The more famous you are, the greater the affect of your reputation?

well idk about the other games but in mm8 it decides who you can recruit (well the generic ones that aren't quest related anyways)

Minor difference to shop prices. I think.

Alright. Thanks for the answers. I had a feeling it might be some kind of score thing or cut material. Didn't expect to hear that reputation gets the boot in the ensuing titles, though. I mean I can't say I'm torn up to hear that I won't have to artificially game the system in an unanticipatable & potentially missable way just to train up one of my skills again, but...

Reputation might affect shop prices in MM7; my brief test showed differences in Harmondale vs Erathia, but that might be as much because the areas have different prices in general (unless you have GM Merchant, of course). Murdering all the peasantry with Armageddon didn't tank my rep in either area, so I'm not sure. Your rep IS area specific though; you can be Liked in one area while having a Neutral reputation in a different area.

In MM8, you always have a reputation of Neutral. I suspect it was simply an artifact of the engine that they didn't get around to implementing, as New World Computing was already in financial trouble when trying to produce MM8.