Zendo, play by forum

[Proxima]

ALEMMING
HLEMMING
SLEMMING

[Ramon]

Nice you managed to generate only black koans

White koans:
  BEFT       FRUIT       MN
  BELTF      FT          OP
  BLEFT      GH          RFUTI
  BUCKLE     HU          RIGHT
  BUCKLES    IJ          SUPERB
  CD         JK          TF
  DE         KL          UPWARD
  EFT        LEFT        UUUUEFT
  EW         LEMMINGF    WE
  FG         LOVELY      XZ

Black koans:
  AB          BU        FEMMING     LM       QR          UV
* ALEMMING    BUBBLE    FLEMMING    NO       RS          VW
  AURA        BUCK      HI        * NOON   * SLEMMING  * WON
  BBBB        BUCKS   * HLEMMING  * NOW      ST          WX
  BC          DOWN      LEL         OCEAN    TB          XY
  BELT        EF        LELT        ON       TU        * YZ
  BLELT       EFH       LEMMBING  * OWN      UB
  BLEMMING  * EON       LEMMING     PQ       UEUFUTU
  BT          FE        LEMMINGS    PU       UP

(U*) and (BU*) is white for H I J Y (and black for every other letter)
(*), (**) and (***) is black for all letters

[Proxima]

This one is very hard and I'm getting nowhere. Maybe it's time for more of a hint 

[WillLem]

+1 for a hint.

[Ramon]

The rule does not involve letter shapes or numbers (that includes the ordering of letters within the alphabet) of any kind. There is an external schema concerning the alphabet you need to know though (and I'm pretty sure you do).

[Proxima]

Lovely puzzle    A koan has the buddha-nature if it contains two letters, consecutive within the koan, that border each other on a QWERTY keyboard.

[WillLem]

Ah, I thought it was something else (which I won't mention in case anyone uses it for a future rule), but a few koans didn't fit the pattern. Well spotted, Proxima!

[Ramon]

Lovely puzzle    A koan has the buddha-nature if it contains two letters, consecutive within the koan, that border each other on a QWERTY keyboard.

Congrats! At first I was afraid it might be "too easy" (especially with all the koans testing each letter with a static neighbor), but as the general rule states, if the master thinks it's "too easy" then it's just right. Seems like it was way harder than I anticipated though!

[WillLem]

Seems like it was way harder than I anticipated though!

It's that old chestnut; easy when you know the answer!

[Proxima]

Next round!

White koans:
TAXING

Black koans:
MAYHEM

[Silken Healer]

FUN
TRICKY

[Proxima]

White koans:
TAXING
TRICKY

Black koans:
FUN
MAYHEM

[WillLem]

AKHBN iff it begins with T

[Proxima]

Counterexample: CRAZY has the Buddha-nature.

[Silken Healer]

AKHTBN iff it's a Lemmings diffuclty level that isn't the first or the last one