As Sandra mentioned in Ansible Core Steering Committee Representative - #9 by samccann currently 3 SC members who can do this (Gundalow, Andrei, me). (I just checked, I have a “Add Users” button, and a settings menu for every member with an entry “Remove Member”, including one for myself 
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I agree with Mario that it’s fine if every SC member can edit membership, since a) we should better trust each other anyway, and b) forum admins can always clean up in case something went south. I also agree that keeping the current situation is also fine, since a) there are several members out of which usually at least one is active who can modify the user list, and b) there’s always the forum admin fallback.
Maybe we should have an informal poll in a few days, if nobody comes up with good arguments for one specific solutions.