The way in which the FIDS (information screens) at airports are now cluttered up with unnecessary codeshared duplicate flight details has now become ridiculous. Some BMI flights in the UK have six or more numbers, for each separate Star Alliance member the flight might connect with.
It is of course well within the wit of those who build GDS systems etc to still show these flights in the current sequence where there are such agreements, or to give the relevant frequent flyer credit, but to stick to one number for the actual flight.
If you are not familiar with the codeshare detail, a rule of thumb is that where multiple flight codes are shown, it is the one with the lowest number of all those shown who is the actual operator. There are some codeshared routes (eg Heathrow to Helsinki, where every flight of both BA and Finnair has both airlines' codes on it) and you do need this informaion to work out who is the actual operator.
Change of Gauge has always annoyed me and I am surprised there have not been legal challenges to its "direct flight (but see footnote)" approach. Worst have always been US carriers on "through" flights from overseas seeming to continue with US domestic sectors. Not only are they not direct, but the through passengers are given nothing more than any other connection to any other point. If the first sector is late arriving the second sector does not wait at all for them.