Originally Posted by
dparkinson
Is this true?
Sounds correct.
When you add a stopover, the ticket needs to be re-fared. Before the change, you are fared as SIN-LAX, which HKG as the connection (tax and surcharges only). With the stopover, you will be priced as SIN-HKG-LAX-SIN.
Originally Posted by
dparkinson
If it is, and I cancel the segment, will it come back in E a few moments later?
Not necessary.
Depending on the travel, some travel can't be ticketed in a particular fare class.