A while back, I proposed giving moderators limited moderation privileges on closely related sites, but it didn't get very much love.
However, this is something that still would be really helpful: particularly on Programmers, where we routinely get people attempting to circumvent bans and rate limits received on Stack Overflow. We have no idea whether a person is actually banned or they just had a momentary lapse of reason, and we waste a lot of time trying to figure it out with very little confidence.
There was a proposal to prevent migrations when the post owner is banned on the destination site, but as I understand it, this only blocks migrations for people manually suspended (something we can already see by just looking at the user's profile on the destination site).
So in lieu of getting limited moderation privileges or blocks on migration for non-public bans, I propose a different feature: when a person gets suspended, rate limited, or low-quality banned on one site, annotate their connected accounts.
This way, moderators can see that a person is banned on the destination site before mistakenly being a party to a ban circumvention.
How about it?