title: Comment belongs_to a deleted user. How to associate a "placeholder"?
body: <p>My comments are placed by users. The Comment <code>belongs_to :user</code> and the User <code>has_many :comments</code>.</p>
  
  <p>But users can be removed. If done, I'd rather not delete their comments, but instead associate their comments with one Dummy user. </p>
  
  <p>I can think of several ways: </p>
  
  <ul>
  <li>On load of a comment, if no associated user is found, create a User in memory with dummy data. </li>
  <li>On load of a comment, if no associated user is found, pick a predefined one from the database. </li>
  <li>On removal of a comment, associate all the comments with a predefined User in the database; through some post filter.</li>
  </ul>
  
  <p>My feeling says that number one is cleanest; since the other two require a user in the database that will be hardwired in the code. If user 18394 will be that "special" user, I'd need all kinds of safetynets for that special user.</p>