Confluence doesn't allow the removal of user who has created any content. The standard method for removal is described in Removing a User. If you want to delete the content as well, the SQL is described below. Locate the content created by the user using the queries:

   SELECT * FROM CONTENT WHERE contenttype = 'COMMENT' and creator = '<Username that you wish to remove>'

および 

   SELECT * FROM CONTENT WHERE contentid IN (
   SELECT DISTINCT pageid FROM CONTENT WHERE contenttype = 'COMMENT' and creator = '<Username that you wish to remove>')

Run the same DELETE commands after verifying the content is indeed content you wish to delete.

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