The LH agents would always comment on my suitcase being over 20 kg; thought they were never rude, I always felt they were doing me a favor by allowing me to check my 55 lbs suitcase. On my last few trips, I always packed an empty duffle bag in my suitcase so that I would check bag and suitcase on the return trip (less convenient for me but, at least, I could be sure I would not incur a luggage surcharge).

If indeed the Most Significant Carrier rule is now in place, that would eliminate some hassle for me and other passengers. That rule makes a lot of sense for people who travel internationally: I find it much easier to handle one wheeled suitcase and a shoulder bag/backpack (from/to airport, from/to public transportation) than juggling with an extra piece of luggage. The main reason I've avoided low cost carriers in Europe is seamless travel on Star Alliance carrier. But if the rules for my 1 hour flight within Europe on LH supersedes those for my 12 hour flight over the pond, then I would be very tempted to evaluate other options.