Some fascinating trivia here! I've discovered a bit of that myself. Nejimakipiyo and I will have to check out the Hamlin/Moonpeta guard's text in the Japanese version. I don't remember offhand how we handled it.
Great to hear you are making progress and joe73ffdq's work has been complementary! I'm looking forward to seeing the result--and I wish I could read it! I have a high-brow friend of mine who is fluent in Latin and I keep prodding him to give your hacks a try. The issue is he hasn't played an rpg since AD&D in the 70's and 80's. A bit of catching up to do.
Here's another bit of trivia I came across today: the game reads controller 2 data after you win a battle. If you win a battle on one very specific but otherwise unremarkable map tile in the entire game (World Map X=$EB, Y=$14, a.k.a. the centre of the tiny "+" formation at the tip of the peninsula near the shrine NE of Midenhall) and controller 2 has the "A" button pressed while controller 1 dismisses the final battle message, the game adds 1 to the battle message delay variable, making all future battles take just a wee bit longer... unless your message speed was set to SLOW ($FF), in which case it overflows to $00 and battle messages become extremely fast. That same variable gets copied and used in a few different places, and various parts of the code only check for the pre-defined FAST/NORMAL/SLOW values, so it is entirely possible that there might be other less-obvious side effects.
I should probably approach this more methodically, but at the moment I'm basically just jumping around to whatever looks interesting and/or easy at the moment. Thanks to joe73ffdq's notes to start with and all the expansion I've done from there, I've got pretty good coverage of banks 4 (battles) and 6 (main COMMAND menu selection handling, which includes the dialogue and searching logic), and I already had the menu data in bank 1 and the script data + text engine in banks 2 and 5; bank 0 is mostly graphics, the rest of bank 2 looks like map data (including warp point data, shared with bank 3), bank 3 is where the audio data lives, and bank 7 has, among other things, the opening Moonbrooke sequence and some text engine support functions. I haven't done much with banks 8 through B yet, banks C-E are empty, and the fixed bank F is a smorgasbord of everything.