I'm a bit over 6'2", my company flies me economy and I can't afford to pay for upgrades myself (though I use points for it, when I can).
I had one bloke react agressively (similar to qwertyplop's experience) after I politely asked him to move their seatback up during meal service, now I ask cabin crew to ask them when my meal is handed to me rather than risk repeating the experience.
One trip I had the person in front slam their seat back as hard as they could, painfully smacking into my knees casing me to double forward. Unfortunately they obviously felt it could go back further so they put it up and did it again, hitting me in the face
. Lady sitting next to me got me some ice (those IFE screens don't give to well) and the (very pleasant) CC who came over to find out why it was needed found me a seat in club.
It doesn't take a lot of effort to consider those behind (and in front of) you and manners usually go a long way. Also try and remember not to sweat the small stuff and it's almost all small stuff.
