I'm finally making some headway with Gallery. After hours of frustration (and annoying Doug) I finally figured out how to get the "Add Comments" link to show up in my theme.
Apparently I didn't need to spend hours digging through code trying to understand the class structures or how the parameter arrays are constructed and parsed. I just needed to use the UI and add "Item Actions" to the list of blocks to show on photo pages...
I still need to figure out how to change those settings through the theme, but at least I have some idea of where to look now. Anyway, now that I've figured out how to get comments working, I should be putting up my photos pretty soon.