I don't know if a refresh when user sign in is enough... 😕
We can have a suggestion from a user, those personal information have been updated on the other system, but until he sign in back to Fider, his profile here is still outdated from others.
We need to find something more periodical I think.

For our use case, this is reasonable (we used to do similar for a Discourse forum, and it seemed to work alright).

If a user wants to specifically force an update (which shouldn't really happen too often), they can quickly sign out and sign back in. Given that everything across fider is tied to a users account (id?), it will automatically get reflected across the site when updated.

I'm not too sure of a case where it can cause a major issue if it's left unsynced for a short while

Given that everything across fider is tied to a users account (id?)

Not really everything: Notifications are stored as plain text. So previous notifications won't get updated. Anyway, it doesn't really matter.

I don't think it's a major issue, but you mentioned the moderation purpose, and being out of sync until the user log in, may be an issue for this. And even if it's reasonable for your use case, we have to think if it's the use case of the most of the people.

Maybe you're right and this is the best solution, I never used SSO so I don't have enough experience I was just sharing thoughts 😄