Are calemondin leaves edible?
This is Texas A&amp;M University's description of calemondin:
http://aggie-horticulture.tamu.edu/patiocitrus/Calamondin.html

In it, they seem to indicate that the leaves are not toxic:


  The distilled oil of the leaves serves as a carminative with more
  potency than peppermint oil.


However, they list just about every use of the tree and its fruit, from marmalades to hair conditioner, and that's the only mention of the leaves.  Because that's the only usage mentioned, I would suspect that even if the leaves are not toxic, they're not suited for flavoring anything.

I hope that's at least a little helpful.