I've added native snails to my tanks in the past but I would never do that again unless maybe I was starting a native setup. If you had pictures, Id like to see them though. I've also mixed native fish with exotics..
The issue with mixing native and exotic species together is that the parasites, funguses, viruses, and..whatnots (for lack of a better word) would be different from what the exotic fish would be accustomed. For example I would never throw a native snail into my tank with Cardinal
Tetras because snails can carry different lifecycles of parasites and bad stuff (again for a lack of better words hehe).
This applies to mixing most native and exotic species, not just snails and tetras.
With all that being said, I betcha most people in this forum have had their "experimental" phase in the hobby.
Jarod I'm in the Saint Louis, MO area and always looking to connect with other planted tank enthusiasts.