Since Joyent decided to end-of-life my "lifetime hosting", I have gone completely bonkers and switched my site to Squarespace 6. (Yes, I fell for the Dan & Merlin sales pitch.)
Somewhere in the course of importing my old content this got confused and old posts ended up living at /oldstuff/oldstuff/numbers/and/things but the blog index page links to just /oldstuff/numbers/and/things (which is actually the correct format).
I'm working my way through fixing them, but it's going to take me a while.