There's a process (/r/redditrequest) where people can ask the admins to assign them as mods of abandoned subs. The existing mods of a requested sub can object,

There's a process (/r/redditrequest) where people can ask the admins to assign them as mods of abandoned subs. The existing mods of a requested sub can object, and it's really only supposed to be used when there is no active mod account, but I'm sure someone will eventually say "they're squatting on the name /r/ProgrammerHumor, can I have it instead?" and the admins will approve it.