Mateusz Konieczny
copy of https://github.com/gravitystorm/openstreetmap-carto/issues/3018#issuecomment-357315185 that is offtopic there:

To be honest, I think this is misclassified, even though the Polish name indeed seems to carry "nature" in it (which is unfortunate).

What "nature" is there a possible 1000 meters underground (except the rare bacteria species able to survive at these depths)? This is a geological monument, not a nature reserve, and as such should likely carry a:

boundary=protected_area
protect_class=3 (Natural Monument or Feature: ... protect a specific natural monument, which can be a landform, sea mount, submarine cavern, geological feature such as a cave or even a living feature such as an ancient grove. They are generally quite small protected areas and often have high visitor value. Cultural and archaeological important. )

and have the leisure=nature_reserve tag removed.

This is also corroborated by this Wikipedia page linked from the tag list of the feature, that talks about a "Polish database of representative Geosites selected for the European Network" instead of "nature reserves".

I also think that whatever measures are taken to not render it, people will likely re-tag it to something that does render, because people want to see this stuff rendered, and certainly if it is a visitable tourist attraction, although this incentive could be reduced by a adding a node with tourism=attraction tag to already have something on the map.