(but quite honestly I prefer how "wikidata" and "wikidata:error" are ordered together alphabetically, whereas "wikidata" and "not:wikidata" are far away)

Yes and no!
I sometimes forget or confuse "not:wikidata" with "note:wikidata" :-/
I made the change changeset/114466963

Hi,
Indeed "name:route" is not a common tag, I used it because:
- Some mappers want to add the name of the route/itinerary, but they use the "name" tag and overwrite the "name" of the local street/road.
The "name" of the local street/road is more valuable than the name of the route/itinerary in my opinion.
- I want to preserve the local name and show to other mappers that the route name is something else and should not overwrite the local one. So "name:route" acts then as a precise "note" to others mappers.

I am aware of the route relations, but "name:route" is a 1-tag quicker fix during some sessions when I do not have the time to create a full route relation.

In any case, even after the creation of route relations, I feel that the note of "name:route" as a mapping warning would still be useful for other mappers in our area.
Otherwise, people overlooking relations might want again to change "name" of all segments with a "ref" to the "name:route".

These tags were not common but have been changed by another user to "not:name" and "not:wikidata".
Re: Wikidata and location
Belle Vue Harel and Belle Vue Maurel are 2 different places in 2 two different districts, but wikipedia and wikidata pages are a mess, where everything is mixed, with either wrong name/district/coord. It is impossible ro refer to any of these pages in their present state.
Most important point: another mapper should not use wikipedia/wikidata to change the name of this place.
node/1133959349
This is wrong: https://en.wikipedia.org/w/index.php?title=Belle_Vue_Maurel&redirect=no