Before changing it, I looked on TagInfo (https://taginfo.openstreetmap.org/) and there were around 675 objects tagged religion=unitarian_universalist and only around two dozen with denomination=unitarian_universalist.

I removed the denomination tag from the few locations where both religion and denomination were the same. I did not change the tags on UU locations tagged with something different, such as religion=christian and denomination=unitarian_universalist.

Alternative tags like geological=mud_volcano and natural=spring with water_characteristic=mud were not very common compared to volcano:type=mud_volcano. Tagging them this way will at least give some consistency, making it easier to retag them when a better solution is documented.

I moved the name to the natural=bare_rock outline of the rock itself, instead of the peak. Perhaps I should have left it.