I think you can input a lower value than .1mm, whether you like the results or not is a different story... The mechanics of the printer may not be up to the task of printing at that height. The nozzle builds up quite a bit of pressure and the lower height you go the more pressure is built up and it is more difficult for the stepper to push filament. Think of a garden hose and put your hand flat over the end at 1", then try at .5", then at .25. It gets more and more difficult, and the water squirts out further to the sides. At some point the stepper teeth are gonna start slipping and eating into the filament.

I print almost everything at .2mm and the quality is pretty good. If there are a bunch of small features I will go to .1mm, but this is rare.