So, I had an issue where text was writing over hacks that were in Kanji space (at least, what is considered as such according to the Kanji Nopper). Where does the Kanji space actually start/end?
**Edit** Patched with Kanji Nopper, patched all my hacks, then applied tactext changes in that order. Opened the Battle.Bin with a hex editor, and found that the wall of 00's starts at E9850. Edited here for future reference.
Not an answer to your question at all but, after every time you apply TacText changes you could re-apply your ASM if they are getting overwritten. That could be a temporary solution :P
You do not want to EVER write hacks to the 1 byte characters (0x00 to 0xCF)... the japanese ones are overwritten by tactext to create commonly used character combinations, like "th", to save space furthermore and allow more text per section. I thought Raven fixed that in the latest version of his nopper. :/
Where font data starts/ends, you can see for yourself which characters would be important to keep:
http://ffhacktics.com/wiki/Font
Where we are supposed to use our hacks:
http://ffhacktics.com/wiki/Allocated_space
Your best friend:
Choto's conflict checker (http://ffhacktics.com/smf/index.php?topic=9897.0) (Although I think he incorporated that one in the newest version of FFTOrgASM)
Hope this helps