Try roughing up the underside of the saddle with sandpaper ie an area that wont be seen. then attempt to polish it back to shiny with progressively finer grades of wet and dry, tcut, 3m etc. if you can get it shiny on the underside, it will obviously work on the lettering.
Ive done it on the back of a kashi, to remove some areas that had been heavily marked, presumably from a fall. the polishing method worked fine, although i obviously had to remove a bit of material with a blade to get the contour of the saddle correct.
on another note, vinylprep, then vinyl cote paint looks very similar to the nylon finish on kashi/elina seats.
