muralito
1. Neither OSMi nor OSME (or any other QA tool) shows all posible errors, they just watch the database for just a subset of them.

2a. "We" collaborate in OSM to improve the quality, coverage, and completitude of the geodata. 

2b. Lots of map providers take the 
OSM data and produce maps, lists, or any other kind of OSM derived information we are not completely aware of, and is this providers (as consumers of OSM data)  responsability for the product they publish.

If you keep 2 nodes and a way for every ford, a consumer looking tio make a list (or just a count) text of ford, will have if for triplicate.