I use tuf cloth on all of mine - they are all users although some don't see as much use as others.
Other than the usual darkening caused by any oily product on micarta, I've never noticed any effect. Washing the handle in detergent has always removed the darkening just as with other oils.
If left on for a long time though, I can't say what effect it might have. I doubt there would be anything that can't be washed off but...
I certainly don't bother about getting tuf cloth oil on the handles but if your plan is to protect the blade before putting on display, then it should be easy enough to apply carefully and not get any on the micarta. Since tuf cloth oil dries, it won't run onto the handle once dried.
Isn't ren wax usually the protective of choice for display pieces though?