Currently leapmotion.pd does not let you know if the hand is a right or left one. This abstraction tries to work around this limitation, but does not fully eradicate it. It ultimately is a quirk, because the SDK should be able to know if it is a right or left hand because of the thumb position. However this information isn not available from within leapmotion.pd
The abstraction has two modes which switch depending on how many hands are in the field of view:
1 one hand becomes present: will check if the hand appeared on the right or the left side from the zenith above the device. Assuming that it is the right hand if it appeared on the right side. You can then use the full space with that hand and it will keep its designation.
Catch: make sure to initialize correctly and always approach the device with the right hand from the right and the left hand from the left.
2 two hands present: will check which of the two hands is rightmost and defines that as the right one.
Catch: never cross hands.