In reality, based on actual experience, I can tell you that it would have worked a bit differently on UA or AA. He would have at least made the flight at the earliest with possibly a change fee.

The reason is that most tickets on AA/UA including the riff-raff fares allow one to change the return segments for a change fee. When in such a position (for whatever reason), I would have called AA/UA rather than be a no-show as soon as my flights from IST were canceled and changed the ticket with a change fee to a future enough date (even if I was not sure which date that would be). When I knew for sure which date I would be able to leave, I would have called again and changed to the most convenient date available. The change fee is not applied again in most cases.

The second thing that would have worked in my favor is that both UA and AA don't zero out all low-fare buckets even if the advance purchase requirements cannot be met for a new ticket. As long as there are a reasonable number of empty seats, they would keep those fare buckets non-zero which would have allowed me to change my ticket to a much earlier flight than what this poster has been able to do.

This has nothing to do with moral/ethical obligations. It simply has to do with providing a service that works for people. There is a reason why so many people who actually travel a lot prefer to fly UA/AA over CO.

This is another example of CO's BUSINESS philosophy intended to inconvenience the low fare customer to such an extent that CO hopes they would never fly low fares again. What do you expect on a riff-raff T fare on CO?