Hate it when I triplecheck all the connections on something and it's still bad. In this case, it was the LCD and I mistranscribed the pinouts. So for anyone else remember it's

1 16

2 15

3 14

4 13

5 12

6 11

7 10

8 9

not

1 9

2 10

3 11

4 12

5 13

6 14

7 15

8 16

So the numbering proceeds in a U-shape, which wasn't what I am used to.

Fortunately, my LCD (shown here) survived the abuse and after rewiring it was fine.