This post box is no longer there. "I'll drive round and check", "no need I'm stood there, it has gone". "I'll drive round tomorrow"...I got the impression i was on someone else's patch and gave up
But with regard to bodies of water, there are systems that monitor OSM and warn if someone has tried to "move them to the right place". These details were often added to OSM from professionally surveyed maps, so they are in the right place. However, ordinary people's consumer GPS is typically a few meters off, and they end up moving things to the inaccurate coordinates on their screens.
Meanwhile, the Dutch community also imports all official addresses, but there the tool simply allows for these to be used with other OpenStreetMap tags. It makes you wonder about the Danish approach.