Hi Moet
It could be possible for you to dislodge the slide cover (bussle) by putting your feet on it (or if you thumped them down for example). Once the cover is off, the slide would be out in the open and the ptotential would then be for the slide to unfurl. This would make the door difficult to get to in an emergency, and might also affect the proper movement of the slide in an emergency to ensure inflation.
The slide bussle keeps the slide nicely contained so that in an emergency it is moved quickly outside the aircraft, the bussle is then opens, the slide falls out, drops the required distance (about three feet) which then triggers the internal inflation mechanism (hence the little red tag to pull if inflation doesn't occur automatically).
All of this is potential - but that is one of the reasons why they don't want you to sit there.
The solution to this problem is to use your carry-on luggage as a foot rest. It doesn't slope like the slide bussle and depending on the model can almost come up level with the seat.
regards
lme ff