Well, I can tell you, Tom, it's what the ink was
supposed to be for the election in Afghanistan [but turned out
not to be], to prevent anyone's being able to vote twice. It basically means unable to be removed, permanent. However, permanently good or permanently bad, is what I'm wondering. "Impressionistic" isn't bad, but "prosaic" means "lacking imagination or interest; commonplace." "Repeated
over and over" is suggestive of boredom with the repetition. "Lurches along" is not necessarily a complimentary image. It suggests being uneven and jolting in sudden thrusts forward. "Unworldly croak" likening how Tom Waits [who already has a gravelly voice] "probably sounds like first thing in the morning" [the 'first-thing-in-the-morning' voice is generally understood to be one that's at least a bit unpleasant]. "Croak" is a word used to describe the sounds that frogs make. It also has an alternative, slang meaning that means to die. "He croaked, you know" would translate as, "He died, you know." A "woozy" melody, likewise, isn't particularly flattering. "Woozy" is generally a term used to describe a woman under the influence of alcohol, or someone [generally a woman, too] who feels sick and [maybe even] about to faint. It could include feeling nauseated, but generally suggests at least a feeling of dizziness.
Geez

.....now that I've gone through all
that, the
only thing I can conclude is that "Indelible" means that it will remain "permanently bad" in his memory; or it was his single-word, coup of sarcasm ~ meaning, "absolutely,
permanently forgettable!"
~ Lizzy