Jumping the gates is a form of trespassing.

This is more like watching the trains come and go, from outside of the station, but ignoring the ads which are painted on the train.

Speaking of looking at printed ads, imagine you had a car which, instead of a windshield, had a high resolution camera and a display. This display would contain image processing which identifies billboards and blackens them out, while leaving traffic signs intact.

Would that be stealing?

Basically, the argument is that not looking at something is stealing.

Where does it stop? What if you're looking, but not processing it congnitively? That must be, in Orwellian terms, a "thought crime": you're looking at the ad, but staring blankly, and its semantics isn't sinking in; you're not allowing the ad to turn into meaning in your mind make you want the product.

The question isn't whether the system breaks down. The question is whether ad-blockers constitute stealing. And they don't.

Not everything that causes a system to break down is stealing. "Stealing" has a specific meaning. It doesn't just mean 'a bad thing happened'.

I think jumping a turnstile is self-evidently stealing. It is also the case that it becomes a problem for everyone when enough people do it, but it would be stealing either way.

So please lay out your definition of stealing and explain why it would apply to this case.

  "take (another person's property) without permission or legal right and without intending to return it."

No property is taken. It's not stealing. There are other correct terms to describe these things like theft of service.

This is some ridiculous pedantry. Theft is a synonym for stealing. Merriam Webster even defines it as the "act of stealing." So if you're going to use "theft of service" as an acceptable phrase, then "stealing a service" must also work conceptually. To complain that is unacceptable to shorten that to just stealing in a conversation is utterly ludicrous.

My definition of stealing includes theft of services.

There is no theft of service until you take a train to another station, and then jump the gates there to exit.

If you want to get around the gates to enter a station without a ticket, you can just ask the staff. I've done it a couple of times in Japan. You can get inside to look for a lost item or whatever. They even let people in to access the station shops. I watched one tourist ask for that and be granted.

Also, one time I entered a station without swiping my Suica card through the machine. I explained that at the destination station and where I had boarded; they cheerfully fixed it up and let me exit. There is room for mistakes without being automatically branded a thief just for being there.

I get the point you're trying to make, but in this case it's me who is paying for the train to move, in the form of internet connection & electricity bills

Those are the things you pay to get you to the station. Those don't pay for the train (i.e. server cost of your traffic).