That's just asking for the temporary fix to never be reverted because the guy who closed the ticket out didn't read it carefully enough. Or the ticket is marked as "fixed" because the workaround works and it has been open for too long. Keep the documentation next to the fix and someone may eventually find it again. Keep it apart and it can be lost forever.
Yes, the ticket should say that. However, if TICKET-432 is still open, and someone from SysOps comes along to make a change to that config file, how would they know that they shouldn't turn on feature-that-should-usually-be-enabled?
They could read through every open ticket to check, but they're only human, and things can be overlooked. If the comment lives right next to option, it's much harder to miss.
Comments are useful for conveying why a particular value was chosen in this particular config file by some person. For example: