It’s taken a while (my fault, I apologize) but we just added a moderator notes functionality for curators as part of a new Moderation History page. Any curator, site admin, or iNaturalist staff member can access this page by going to a user’s profile, clicking on the Admin Tools menu and selecting Moderation History. No one but staff members can access their own Moderation History page.
Here’s what that page looks like for a test account:
Any flags on the user’s content, any moderator actions taken (which right now is just comment hiding) and any moderation notes about the user are shown on this page. There are filters at the top if needed.
Curators, site admins, and site staff can now add a “moderator note”. Moderator notes are short notes describing any sort of action taken that’s not obvious in flags or other actions (eg messages to the user), responses by the user, or evidence-based concerns (such as whether the account might be a sockpuppet). You can see two examples for a common situation above.
I really want to emphasize that moderator notes should not be used to opine about a user - they exist so other moderators can see which actions have been already been taken. Discussion should happen on flags or, if privacy is a concern, via an email to email@example.com.
Hopefully this will help keep curators on the same page (so to speak).