Board Thread:Support Requests - Community Management/@comment-26382471-20151122205012/@comment-27221424-20151122210018

I'm not sure on the technical side of things, but some wikis have a system in place so that if the user in question does not log in within a certain amount of time they are considered to be inactive. If the bureaucrat had stopped editing "a long time ago" as you said, I imagine it would be fine to use their characters (depending on how long a long time ago is, of course).

Other than that, you can hold a community vote to get the demotion in the queue so it can be "official" (this does not apply if they return of course!) All in all, it comes down to your inactivity policies. Best of luck!