title: Who or what is '_mbsetupuser'?
body: <p>In all my terminal sessions on OS X or macOS, if I type <code>who</code>, in addition to the expected users (all me in various windows) I also always see</p>
  
  <pre><code>_mbsetupuser console  ... 
  </code></pre>
  
  <p>Just <em>who</em> is that, and what is he/she doing?</p>