In the general case you can look at taginfo and click through to Overpass, but with 464,958 uses you’re going to get a lot of mappers. Here excluding crossing:markings might help, but you’ll still get an unfeasibly large number of mappers. You can use Overpass to break down the list, and maybe sample it to find some only added recently.
Identifying data consumers who publicly record what tags they use is easier - the taginfo project list shows four, atthough the iD** comment is a bit cryptic, so it’s unclear how it will appear there, but the others are more straightforward. Many data consumers don’t record the tags they use, so identifying them is harder.
** but entirely in keeping with the dadaist nature of the iD project