Of all the expeditions to the wreck, I do not believe any mention was made as to whether the stern letters were visible, from the looks of it a waterfall of rust obscures them. However faint outlines of the bow letters have been seen.
There are several Titanic books which have pictures of the bow letters, though I believe only the second "T" and the "C" were visible, but this was in 1985 with all the recent state changes and hull deteriorations they may no longer be visible. As for the stern wreckage, I have seen some pictures of details on the web but not a complete stern picture, sorry I misread your first post when I replied.
You can find photos of the Titanic's bow in Triumph & Tragedy and there are a few in Illustrated History - beware the photos of the ship in the stocks however, the name has been added after the photos were taken, TITANIC wouldn't appear on the real ship until it was in drydock.
I have seen a video of the bow letters. I could make out a T and IC. I could not tell which T it was.
In Robert Ballards book he says the overhang of the stern is at such an angle that rusticles dont grow. Or there arent many on it.