Q&A for SharePoint enthusiasts
SELECT UserId FROM Comments GROUP BY UserId HAVING COUNT(*) = ( SELECT MAX(CommentCount) FROM (SELECT COUNT(*) AS CommentCount FROM Comments GROUP BY UserId) AS Counts ) AND MAX(Id) IN ( SELECT MAX(Id) FROM Comments GROUP BY UserId HAVING COUNT(*) = ( SELECT MAX(CommentCount) FROM (SELECT COUNT(*) AS CommentCount FROM Comments GROUP BY UserId) AS Counts ) );