See [[ https://en.wikipedia.org/wiki/Wikipedia:Village_pump_(technical)#Permissions_pop-ups? | enwiki VPT thread ]].
I tested it to accept and it worked for me, but not for the reporting editor.
I have received a Permissions error page atleast once in the past stating only Pending changes reviewers and Editors could carry out the action.
I tested it to unaccept [[ https://en.wikipedia.org/w/index.php?diff=938845132&oldid=938826731&diffmode=source | this revision ]] and it did not work for me. The diff also says "Accepted by Cyphoidbomb" although it should say "Automatically accepted" as they are a privileged user (administrator).
Edit: Adding WM-site-requests in case there is a local wiki configuration error somewhere.
I'm guessing this can be resolved by adding Administrators in the usergroups necessary but that should also be the usual for all wikis (I presume).