Is this EVSE compatible with my 2012 Leaf?

It is true that an EVSE that is connected to a higher power circuit will work fine. A 16A EVSE will draw 16A from any circuit that exceeds 16A. It will still draw 16A from the spec max of 80A.

To avoid over heating and fulfill the NEC ratings is must be greater than 20A (16A is 80% of 20A).

Asdsuning enough current is available the Car sets the current. If less is available then the car will match the available current. For example a 16A EVSE needs 16AIt can operate from any source that will supply at least 16A. My EVSE runs on a 50A breaker. It would accommodate a Volt at 14A but the rest of the 50A is wasted. I charge my Mercedes B at 40A on a 50A circuit. 40A at 80% maxes out a 50A circuit. My B charges at 40A but the EVSE would be happy to charge an enhanced Leaf at 27.5A The rest is unused..