I wrote about this a while back, but I didn't realize the extent of the problem until I tested this further.
When spells are reflected, the counter script doesn't always execute properly. When Holy is bounced from a Wall onto a Behemoth in FF4, the Behemoth doesn't respond at all. In FF4A, it produces the proper counter of Storm.
Edit: Corrected the reaction the Behemoth does.
So, apparently there's a bug with it... but it's a little more than that.
I did some interesting testing with HP based counter scripts (HP dependency like Kainazzo/Cagnazzo).. and apparently the monster
does not react properly to reflected spells either (he didn't change form when lightning was reflected), but also that he had low enough HP to trigger the "shell mode", but he didn't change there either. So, it is actually possible to say kill Milon-Z/Scamaglione before he changes to Rubicante (I've tested this, and this actually does occur).
This Reflect-Counter behavior is broken in the SNES versions, but is fixed in GBA versions.
Here's a pic that's normally not possible, but is actually possible to due this bug...
Ignore the party, but look at the HP display. Cagnazzo/Kainazzo is supposed to be in "shell mode" but isn't.
We have EVEN MORE themes now, but some old ones are gone...