[RegW]

Sorry, I don't have an answer, but I just feel the need to say that OSM isn't alone. Google doesn't handle it any better when it comes controlling poisoned data.

Some years ago, in my town some moron (probably in some half-assed attempt to get the town council to deal with its incredible lack of cycling infra-structure), managed to mark pretty much every pavement as a cycleway. Of course the effect is to present the town to potential visitors as very cycle friendly. It ain't - but the council don't care.

I submitted a number of notifications to Google via the appropriate link. Even attaching screenshots from StreetView showing the "No Cycling" signage. The only response was an automated reply. Years later Google is still showing these non-existant cycleways, so I assume that all notifications of incorrect data go straight to /dev/null.

Edit: perhaps the answer is for OSM to provide a downvote button for bad features.