Jan 09, 2017 - 01:47 PM
The threads on your toilet fill valve are often quite long to make sure that a) it protrudes far enough out of the toilet tank and b) allow enough space for any supply line to be threaded on, so yes, there should still be threads showing on the fill valve even with the adapter installed.
When installing your bidet, due to a meriad of reasons like imperfections in the toilet base, your bidet could not fit perfectly flush. We used to carry thin rubber bumper pads but no longer. These can be easily acquired from any local hardware store for very cheap to level that out.