actually the more i look at it it in part looks like the lines/smudges could be part of the light reflecting internally to the wedge off the bevel that is all around the edge.
maybe its hitting that and bouncing around a bit to create the appearence of light and dark banding within the plastic iteself....
dunno hard to say.
on the tape issue....heh funny been thinking exactly the same....contemplated (breifly
about just using a black artline to carefully colour in the edge to stop the 'bleed' of the light around the top and side edges of the wedge.
ideally as others have suggested would be a reflective colour/cover on the edge and then black over that to colour code it to the reader a bit....
dunno have to think about it a bit...due to the wedge being plastic and the edge being roughened anything like a marker etc will be pretty hard to remove and cant just wipe it down with metho etc without being careful.
obviously the ideal would be a prs-605 that has the light wedge integrated into the reader itself....some may not go for it as it would cause the reader to be not so slim but could be a more elegant solution than that of the external light (not that im complaining that they went to the effort to make one).
anyway....overall ive tried it again last night for an hour and i think im getting used to it....is less distracting when you dont pay so much attention to it so cant complain too much.