Baggage overweight?

So further to my enquiry before the trip,what actually occurred was……..
After getting the views and advice on this forum, we put our heavy,rigid,Carlton suitcases aside and purchased light sports bags which increased our carrying capacity by at least 15%. Anything fragile was carried in our cabin bags – which on Lufthansa can be 8kgs.
We checked in at LHR with 78kgs between the three of us with no comment at all from the check-in staff.(With whom we had discussed the Braun fuel cells before check-in).
So that was a relaxed check-in,but after a considered “what can we expect to be acceptable over the 20kg limit”.
Can I raise a point regarding the “abuse” of allowable cabin baggage?
There were some very upset pax on our FRA-LHR sector who, having flown in with large cabin bags from BKK or MNL, were not allowed to carry them onto the aircraft when they reached the boarding gate. Comment overheard from the boarding gate staff was “I don’t care that you were allowed to carry it before – I am responsible for this flight and I have decided you cannot take it.” Now I know you cannot really argue with that, but if it were mandatory to “prove” the bag in the testing “apparatus” then we would all know where we stood. It might also prevent occurences like the one my wife experienced on boarding a BMI flight to PMI when she had her bag taken away with the remark,”It may be an acceptable size,but we are not taking any trolley bags into the cabin today.” Crew included? Well, try that one on us again and I will forfeit the cost of the ticket to get the satisfaction of being as awkward with you as you are with me – take off my luggage, I’ve decided not to fly with you today.
However,just to ensure that I don’t give the wrong impression, I must say that I found the Lufthansa staff in LHR,FRA,&MNL friendly and competent.So there!