If you're curious about what healthy HoF data looks like, here's a picture:
The formatting is simple enough. Each Pokemon gets 16 bytes. One for species, then one for level, then eleven for nickname, followed by three nulls. Any leftovers in the nickname are filled with end-string characters (hex 50).
The HoF data pictures will display:
A level 6 Charmander named CHARMANDER
A level 12 Rattata named Mutton
A level 4 Rattata named AAAAAAAAAA
A level 3 Mew named MEW
A level 40 Cloyster named NAUGHTY
A level 21 Magikarp named MAGIKARP
If a team has less than six pokemon, the empty slots will still be occupied with data, with a species value of FF. There is another byte, at 284E, that seems to determine the number of E4 victories. I can't test this, though, as changing the byte causes the save file to read as corrupt.
You might also notice that the 256 bytes before the HoF (which I am affectionately calling the "Danger Zone) is filled with FF in a normal new game. I'm not certain if this is changed over the course of the game, as I (obviously) used cheats to beat the E4 early. If anyone knows about this, or has a late game save file that has never encountered a glitch pokemon, feel free to let me know.
Well, my memory map now looks like this:
As you can see, the mass amount of bytes before and after the hall of fame data (even before 0498) are also filled with garbage values. I haven't beaten the E4 yet (only have 6 badges). I didn't use cheat codes in this save state, and I have only caught (and encountered) A, h Poke, LM4, Ghost sprite Missingno., some other normal Missingno. I'm currently standing just outside the Safari Zone gatehouse, with the 500-step counter activated (still studying glitch maps) and having flown away from the Jr. Trainer in Route 24. I've done ZZAZZ in another save state (deleted).
None of the above glitches should affect the area before 0498, if the supposed affected area is correct.