One of the reasons "droll" is a good candidate for this list IMO is because one can almost always hear the invisible air quotes (those guillemets or guillemots or Gänsefüsschen) the speaker places around them.
I think "quaint" is a candidate for much the same reason. Certainly, when used in the phrase "How quaint", the implied meaning is almost always pejorative.
In my experience "droll" still means humorous or amusing. It's sometimes the case that the word is applied with a condescending tone, as if the speaker is acknowledging the humour but doesn't quite want to admit to finding it funny. (This, I think, is very different from using the word to mean boring, stupid or humourless.)
But mostly I hear it used (when I hear it used) to acknowledge what the Shorter OED calls dry, whimsical humour, odd or unexpected. And in that context it is perhaps the greatest compliment to describe such humour as "droll" rather than the more mundane and less accurate "funny".
I really don't recall hearing/reading the usage that pterodactyl describes. Perhaps I should get out more
I use the droll tag here — and the word more widely — quite sincerely, covering both those two senses, I suppose (I'd not looked it up or thought about it before, but it does match my usage of the term): never as an insult, mild or otherwise. It does carry a connotation of recognition of a rather bad joke, but I have a lot of love for those.
I think it depends whether you like drollness. Some people find it clever and cute, others find it stupid and cloying. OED2 recognizes two senses of droll: "Intentionally facetious, amusing, comical, funny" and "Unintentionally amusing; queer, quaint, odd, strange, 'funny'."
Well, it's hard for me to describe, mollusque, but what I'm looking for are words which are never used literally, but only ironically. In all my life I've never heard "droll" used literally -- every single usage I've heard has been ironic.
It fascinates me that this is possible. Irony only makes sense if you know the literal meaning of the word you're using ironically. With the literal meaning of "droll" being pretty much dead, how is it that we're still able to use it ironically and be understood?