Custom Social Interactions with XML tuning?

I have heard that it is possible to make custom social interactions with XML tuning, but that it comes with the cost of incompatibility with other people's mods. Could someone explain exactly what kind of incompatibility that would be? And if it's really better to use Python, I'd like suggestions on simple absolute-beginner tutorials on how to use it to make a custom interaction.

I am talking about social interactions for Sims. Specifically, I have a custom trait and I'd like to have Sims with my trait have special friendly interactions that only they can do, the way that some traits, say Music Lover, can "Discuss Favorite Band" or Geeks can "Enthuse about New Show." There are a few tutorials I've found that deal with adding interactions to OBJECTS, but I haven't found anything that's for social mixer interactions.