Alright, after some discussions with our legal counsel, we’ve decided that it’s too difficult for us to verify that a deceased person is actually the owner of a specific account (in our records, we don’t have much more to go on than an email address and username), and thus we won’t be supporting a public-facing way to denote that a user has specifically passed away.
Rather than deceased, we will look into implementing a way to indicate that a user has not been active on iNat in a long time, or to easily see when they were last active, a request being discussed here: https://forum.inaturalist.org/t/make-it-more-visible-throughout-the-site-when-a-user-is-active-within-last-week/142/8