As described in T353805#9420785 this feature is useful in sockpuppet investigations, when we have accounts hunting for a specific mentor. There are several non-exclusive ways to go forward which would still be acceptable in my opinion:

• aggregate opt-outs followed by an opt-in in a single change (e.g. from mentor A to mentor B instead of mentor A -> none -> mentor B)
• expose in GUI a way to directly change the mentor to another - I understand this is already available as an API call
• limit the visibility under a userright that would be assigned to trusted user groups (e.g. patrollers and admins)

The opt-out feature was originally added by T&S request to mitigate risks involved with letting mentors easily watch their mentees (via the Mentor dashboard, for example). I think logging opt-outs publicly negates that purpose. That being said, logging those events privately (in Special:CheckUser only?) is likely not going to be an issue. Whether a sysop-only or a patroller-only log level would be sufficient, that's something for T&S to clarify.

CC @KStoller-WMF as Growth PM in case she has any thoughts and moving to Triaged for now.

In T353931#9442206, @Urbanecm_WMF wrote:

I think logging opt-outs publicly negates that purpose.

Isn't this information already publicly available through {{#mentor}}?

Also, do you have any thoughts on my second proposal (changing the mentor from GUI)?