I found this on internet:
Waypoints names can be up to fourteen characters long. Comments can be up to 30 characters. It may look like there's more space availble for waypoint comments in the window, but 30 is the most stored. For longer names (if you're willing to give up creating/editing on the device itself and use a computer) investigate custom POIs
It is very very very sad that you cannot insert more that 14 characters. Have anyone a solution for this problem. I find this a real problem and it made me sad!!! It is very pity.