I would think that depends on the mods. If you apply grip to the comtroller, it's now modded but why would Bungie disapprove? You can use a tap set and threaded plugs to make trigger stops. Or you can use a Scuf controller that already has them. Option A is modded, is it frowned upon? Is B? A lot of ways to mod a controller to make it more comfortable or more personalized for ease of use and accessibility.