Reserved seats - you are entitled to have them moved, sometimes easier said than done on a crowded train.
To ease your angst, allow me to share my pet hates that I endured through many years of commuting
Men with broadsheet newspapers or bollocks so large they had to spread their legs or arms to the width of 2-3 seats
Men (well, women if they did but never had one do this) who would burp "politely" you'd hear then burp, mouth closed, hand over mouth) who would then "release" the burp, and puff it across to the poor person opposite (me). Usually smelt of salami, beer, or beer and salami. Or both. Lol.
People who would lean to the side to fart silently, and you'd think, why are you leaning to the side, hell, perhaps they have had a stroke or heart attack, then the fart smell would hit you.
People with long legs - shame for them, really I'm not bitter, but do you have to physically kick my little feet out of your way so you can stretch your legs in between mine? Seriously?
The Rucksack. Grateful you are willing to stand, not that you had a choice, but if you whip around to change direction, please be aware that the 30kg of luggage you hold on your back has broken my nose and given me concussion. No, its fine really, just be aware.
Phone conversations. If you must, put them on speaker, because it is incredibly frustrating when you exclaim "NO! SHARUUUP! YOU DIDN'T! FAAARK! REALLY?" and not know exactly what they did or didn't do.
Yawning. Yes, commuting is boring. Do not puff your yawn my way. If you must, one word that springs to mind is floss. More than once a week, please.
Snoring and snorting - nuff said.
That might do for now.