So I broke down, and did in fact rip back the Black Purl sock back to the toe. Then I re-knit it with the proper zig-zagging twists — and I re-knit the heel — and I re-knit the eye-of-partridge heel flap — and then I ripped that out, having forgotten, once again, that stupid zig-zagging twist on the heel-flap! Once ripped, the heel was all knit again… only the twists didn’t quite line up the way they should. There was a period of most unladylike language and some cruel wielding of a crochet hook and eventually things were done properly.
Here is where it’s at now:
Apologies for the craptastic night-time photo.
It really just looks like it did in the last photo I posted of the sock, only, y’know, proper.
A close-up of what all the fuss has been about: a toe-up, gusseted, slipped-stich (eye-of-partridge) heel-flap, with the addition of the continuous zig-zag twist:
In fact, this heel fits really well. I’m still not sure if that makes up for how many times I’ve knit the thing, but it does fit really well.
If I ever think that I can improve upon a beautiful-looking pattern again, or am trying to be stingy with my yarn, I’d like to think that I will remember the troubles I’ve been through with this sock. But I know I won’t — one skein of autumnal STR, to toes knit, the rest in a bag, awaiting the ‘perfect pattern’, says otherwise…
Aemmeleia's Ephemera 
Congratulations on sticking with it and getting it right. I gave up on this pattern because I decided it didn’t work well with my yarn. I’m glad you’ve stuck all of this out because it is a beautiful pattern and your sock looks great.
The sock looks awesome! The yarn and the pattern complement each other very well. Good job!