A common suggestion that is MattHaughey should appoint more moderators in addition to Jessamyn to help him with the running of the website, but MattHaughey has consistently disagreed with this. So the primary mode of 'policing' MetaFilter for posts and comments that are deemed bad is simply self policing. That is, members of MetaFilter will, upon seeing a bad post or comment, try to talk to the user in question (usually by posting a thread in MetaTalk) and sort everything out without recourse to MattHaughey.
Flagging posts and comments to bring them more quickly to MattHaughey's attention is another, relatively new method of 'policing' which keeps MetaTalk from being overrun with complaints.