It’s not quite summer yet but I’m going to nominate @finalsummer anyway (MB profile)
They’ve been a part of MB for almost a decade and over time seem to have gotten accustomed to the database, guidelines and its quirks.
They are more or less active on the forum and hang out on IRC. Occasionally participate but mostly seem to monitor what’s happening.
Lots of accepted edits and even more auto-edits. A couple weeks ago I’ve noticed that they upped their voting game, providing pointers or making follow-up fixes and No votes seem reasonable.
Now, for some this might seem a controversial choice as there is a considerable amount of voted down edits. Quite a few of them are either old, those I’m not concerned about or were part of other edits.
Where the guidelines were less clear they are arguing their case, not shying away from going the extra mile