@davidfor: I'm certainly not going to argue with you on that one: I hadn't touched that patch in over two years, and was living with a vanilla Calibre build just fine, only getting moderately annoyed every time I dug up the PW2

.
[Speaking of: I just squashed stuff on GitHub to make it slightly easier to review].
But now that I know it can be done properly, I'm pretty glad I looked into it again

.
And we do have a few people who do care about it (hi, @jackie_w

).
(FWIW, with all the bells & whistles enabled (i.e., PNG), it does generate slightly smaller files to boot, on the whole

).