Redundant Tags + Confusion
I looked how this tag was used and it seems like 99% of the time it's just and addition to club= for no reason. http://overpass-turbo.eu/?key=leisure&value=club&template=key-value
A generic first-level club tag could be used to identify a club base and provide an easy identification even if the club value is unknown, uncertain or rare.
- identify a club base - Great idea. But not helpful when the tag can used for different stuff, too. I would suggest something explicit like club:hq=yes
- if the club value is unknown, uncertain or rare. - club=yes done. The same amount of information as leisure=club. We do it exactly the same way with buildings. This will encourage mappers to find a value in the first place or other mappers will see the yes and be encouraged to find something better.