Hi, I don't use Wikipedia often, so I don't know if this is the place you wanted me to talk about these topics. Anyway, here are some things I wanted to say.
There should be only one OSM object (relation, way or a node) with a unique wikidata=* tag. You can't have several Danube rivers, there is only one. We should decide which OSM object should be representative of the whole feature. With rivers, it should probably be the relation that has all the centerlines ant the tag type=waterway. So you should put the wikidata ID of Danube on the Danube river relation , and nowhere else.
Tunnels should have their wikidata=* tags on areas that have the tag man_made=tunnel, like the Gotthard Base Tunnel . That tag is not used much, but roads going through the tunnel are not the actual tunnel. That's why they can use tunnel:wikidata=*. You can have more of those.
That means that the Disney park shouldn't have that Wikidata ID. That specific park is not described in that Wikipedia page. It's just the same design. So you can be creative and put something like design:wikidata=* or something like that.