As I checked in at the airport I asked what was up with online check in. Evidently a computer glitch: the flight had never been released for online check in. The airport staff noticed this and called in the problem.

So there are two software issues here that could be improved:

(1) the system that sends emails advising you to check in online should not do that if the flight is not available for online check in

(2) the message about "restricted to gate" should say "restricted to airport"

Not the end of the world, but getting the little things right saves a lot of grief for the customer service staff...not to mention the customers