As a guard I'm a bit of a
"luggage nazi". No luggage in the doorways, aisles, or vestibules. No luggage in the disabled areas. No wheeled or heavy luggage on the seats. This is regardless of how empty or full the train is. I charge a luggage ticket is there is space in the rack but the luggage is in the aisle. I charge a full single if the luggage is on a seat - and inform the passenger that they will have to remove the luggage if a standing passenger wishes that seat.
I've had two on train fires & know the importance of keeping all exits clear. Common sense really.
Wish regard to soft bags,coats, &c. I don't mind if it's quiet but if my train starts to get busier then I use the P.A. "Ladies & Gentlemen this train is now rather busy & we expect more passengers to board at the next station. Kindly remove all items of luggage, coats, newspapers, &c. from the empty seats beside you. You will find plenty room for these items in the racks above your head. This allows your fellow passengers to take a seat"
Of course if that is not heeded then stronger action may be needed. Don't get me started about feet on seats...........