Tapeti has a fetish that is a hard limit of mine.
It's not a fetish that she wants to inflict upon me, so we're not going to run into troubles there. However, I was very surprised when she expressed her desire for it; even though I understand that there are lots of people with desires that are starkly different from mine, for some reason I still expect everyone I'm sexual with to be perfectly compatible in every way.
I'm not sure why I feel this way - even Master, who's probably the most compatible of my partners ever (most likely because I basically discovered my sexuality through him, so I "imprinted"), has some fetishes that I'm not so keen on, and I have some that he's not into. It's not a big deal, so maybe that's why I'm always surprised; I forget that those differences exist because they don't have any negative impact on my relationship.