I've done more research into Saihoji during the past two days. Apparently, people not being able to resist the desire to pet the moss was such a problem that they closed the temple to the public for more than a decade. They just opened it again in 2023, but you have to go through a very long (and very Japanese*) vetting process to be admitted.

It must be difficult for that moss to be so green and so soft and so fluffy.


* By "very Japanese," I mean that postcards and fax machines are involved.