Retaining a value after hiding and un-hiding a field

We have a screen when we hide/disable a comment field based on a value in some dropdown. For some values of the dropdown the comment is shown, for other values it's hidden. For example, imagine a dropdown with a value "other" where for other the user can freely add some explanation.

Now, imagine the following scenario:

  1. User selects "other"
  2. User adds a comment
  3. User selects a different value that hides the comment
  4. User selects "other" again, so the comment field is visible again

What shall be the behavior of the comment field - should the comment from step 2 be retained or should it be empty?