OK, this is getting close, I like it. Thank you@modemlooper, and apologies to @Henry for misunderstanding.
Some features are disabled, which is great, but a read-only account can still comment, add files to the file repository (Multiverso plugin), add a calendar event, upload photos to the photo album and edit (but not create) wiki articles.
We don’t have a verification procedure on our website (it’s private) so I don’t think this would apply. If you think this is relevant and that I should put some kind of verification procedure in place in order to get this working, please let me know.