It is not that hard to fix duplicate nodes. In JOSM, find them with
the Validator plugin. Double-click a duplicate node warning in the
validator error list and hit 3 to center the map at the nodes, so that
you can check what to do. Then hit M to merge the nodes, unless it
is something else (tunnel or bridge needed, for instance).

Validator plugin comes up with lots of false positives (like duplicated nodes one in a way and the other one in a city/county boundary) and is about useless for that purpose in the US.

N.