Major ones to know for playing the game well:
* the index in the weapons table is used rather than the value in the table, making later weapons much more powerful and making Axes (lower %hit, higher critical%) useless.
* No secondary effects of weapons work at all
* Intelligence has no effect on spell effectiveness (yet another reason why red-mages are more powerful than they ought to be)
* All enemies are immune to poison.
Interestingly enough, people have created patches for most of the known bugs!
https://www.gamefaqs.com/boards/522595-final-fantasy/4557505...