I'm glad that yorkie has found my recent post on this matter. It really isn't an issue worth any further thought, assuming that there is nothing else untoward about the journey.
As for asking staff en route, then the majority of long-distance services on the ECML which go on to Haymarket will have a change of guard at Waverley, and who will not be inspecting tickets between those 2 stations. Gateline staff at Haymarket receiving a ticket to Edinburgh will not be interested. The place to be concerned is the barriers at Waverley - you will normally be passing through the 12 - 18 barriers to board a Scot Rail service, and may have arrives on the southern island platforms 8 or 9, which often have human barriers. If you are polite, confident, friendly and open, then they are unlikely to want to delay you a moment longer.