Ah yes, this game still exists...
The rule was: AKHTBN iff the 3rd letter matches the 3rd letter in alphabetical order (and the koan has at least 3 letters).
So for example (going back to the initial koans):
AL
ABAMA – AA
AABLM has buddha nature
MI
SSISSIPPI – II
IIMPPSSSS lacks buddha nature
Floor is open, let's revive this great forum game!