I was able to hack the prototype to insert an N MOSFET between the two Ps and now the behavior of the HV !RESET jumper is correct. It's effectively floating normally, and then has 12 volts switched onto it when the incoming !RESET line is pulled low.

I've also validated that it actually works properly with a real device. I've turned the RSTDSBL fuse on and off several times in a row, verifying that programming doesn't work with the fuse on and the adapter's jumper in the NORM position.

So the boards I've already ordered from OSHPark will work correctly.

For my own part, I intend to just leave the jumper on HV permanently. This does behove you to insure you don't attach the programmer backwards - that would impose 12 volts on Vcc for the duration of the programming attempt, though ground would be hooked to TPID, so that may not be completely tragic.

As soon as I build the next board, this will be added to Tindie.