This is very interesting. This implies that the computer will enforce the int'l rules (which would normally be ticketing deadline at 60 minutes, seat assignments released at 40 minutes, and reservation released at 20 minutes) for the initial domestic check-in.

In addition to having to rush to the gate to get this straightened out, you risk losing your seat assignment (and your reservation and denied-boarding compensation if the flight is oversold).

Also, there's the problem of what to do with your checked baggage if you have to check in at the gate. If the baggage is too big to fit through the x-ray machine, or if it is obviously too big to carry on even if it goes through the x-ray machine, you can't proceed with it past the security checkpoint.

This situation happened to me once. It wasn't an int'l flight, but I was on standby for a domestic flight. I had an oversized garment bag that clearly is too big to carry on, but it would fit through the x-ray machine. The security supervisor stopped me and told me I had to check it. I told him that I was planning on gate checking it. He would have none of it, and sent me back to the ticket counter. I had to check it in for the flight I was on stand-by for, so it would have gone on that flight whether or not I cleared the waitlist (which thankfully I did).

The moral of the story: missing the check-in deadlines, especially if you have bags to check, isn't a good idea.