Originally Posted by pauldb

The clause you refer to is about changing fares, not cancelling segments as a penalty.

It simply prevents an argument when someone thinks they can change a fully-flex LHR-JFK-LHR into JFK-LHR-JFK without paying the different fare. This is what is termed a reversal. Adding a seperate ticket which takes you back to the same country/city is not a reversal, and as such this clause has no relevence. It is however a case of nesting, which potentially they could pick up on.

They might do this is they thought you were messing them about, but I think the general experience is that it's highly unlikely. You should technically hold tickets for LIS-LHR-JFK-LHR and LHR-LAS-LHR-LIS for your itinerary.