I wasn't trying to solve that particular problem, on the assumption that it has already been solved and the same solution can be adapted to the implement I proposed. Someone else who replied to me suggested something like requiring majority approval to add or remove a mod.

Another possibility is for the creator of a community to be a super mod, who can add or remove regular mods, or transfer their super mod status to someone else. That scheme could easily be generalized to allow multiple super mods, or to include a whole hierarchy of mods for large communities.