How to annoy a Londoner. Stand on the left on the escalators.

There will be tutting.

I didn't put the whole quote on the Pincard, but here's another bit of that:

There are plenty of areas in which Europe has cornered the market on stupid, but somehow many Europeans seem to get it about moving walkways and their older cousin, the escalator: Walk left, stand right.

In a lot of U.S. airports (e.g, most of the ones at Hartsfield-Jackson), the escalators are not wide enough for one person to pass another, unless they are both very skinny. This is especially true when they are both toting bags.

How to annoy a Londoner. Stand on the left on the escalators.

Same with a lot of subway systems. And sometimes the "left standers" will get a lot more than tutting.

In a lot of U.S. airports (e.g, most of the ones at Hartsfield-Jackson), the escalators are not wide enough for one person to pass another, unless they are both very skinny. This is especially true when they are both toting bags.

I still make an effort to stand all the way to the right and put my bag sideways on the step ahead of me, right up against the right wall, just as a courtesy. If someone with nothing but a briefcase or backpack is rushing to make a flight or a terminal shuttle, they still have a couple feet to dash up or down on the left (at least in some airports -- as you say it depends on the width of the escalator).

Some comedian, I think it was Jerry Seinfeld, said something like, "It's not a theme park ride. Keep walking!"

tut-tutting? Hell no! I usually bellow:

"STAND RIGHT! WALK LEFT PLEASE!"

They get the message very quickly.

Only if it is someone I see might be having problems, such as someone with a cane, an elderly person (must be VERY elderly), or someone holding a young kid's hand will I NOT say something when "left-lane dicks" block an escalator in the NYC subway.