I had a bad experience with a J1772 charging plug pictured here:
(The upper one with the grey plastic body and orange cable. The lower one in the picture is the Nissan supplied Level 1 unit. The difference is clear.)
When I plugged it into the port on my LEAF, I could not get it to release, no matter how hard I tried. And I TRIED. The problem was that the mechanical catch mechanism doesn't have enough range of motion to release from the LEAF port. It will click into place when inserted, but it won't move upward enough to release when you press the release button and pull back.
This took the better part of an hour and involved quite some anxiety and partially disassembling my pristine new LEAF.
To make matters worse, this connector has a hard plastic hood that covers the catch area and prevents the insertion of any tools to help pry it loose. (Fear not, it wasn't energized.)
The final solution was to remove the four bolts that hold the charging port to the LEAF body so that there was enough clearance to insert a tool. The successful tool turned out to be a right angle screwdriver.
I have edited the wording at the beginning of this thread. I had a bad experience with the connector pictured, but I have no evidence to conclude that all J plugs that look like this will not work or will not release properly from a LEAF charging port.