I don't think that they were claiming that it was illegal to do that. They claim that extension breaks their ToS, which is a private contract.

> their ToS, which is a private contract.

the ToS is between a facebook user and facebook, not the author of the extension and facebook. In fact, the author has no obligation whatsoever with facebook. If facebook does not like their site messsed with, they could detect and block this extension like how some sites block users with adblock running.

Facebook doesn't need to have a reason to ban you from their site. It's their site.

Yes. They can ban anyone they want. My question is how they know that Facebook user X and browser extension Y have any connection. If the extension's maker was marketing on Facebook, he should have expected this.

Meanwhile, yes, the TOS is between the user and the site. If Facebook wants to fight its users and say "if you don't send HTTP requests for our ad images, we'll stop answering your HTTP requests for our HTML pages," that's up to them.

I do think we need to push back whenever companies assert a right to control how a user views their site. That is fundamentally not how the web works. Every resource my browser requests, it requests by my implicit command to do so. Nobody has the right to tell me what to request; they only have a right to decide how they'll respond to my requests.

They made the connection because he was using Facebook itself to market his extension. I suspect that if he hadn't been doing that they would not have banned his account.

It doesn't make it right, but it does point out that future FB-extension developers should be cautious about connecting their FB account to their extension.

Yes, yet I don't see how they could have something in their ToS that says "you can't change the appearance of the website" since each user can see a website however he wants (Facebook does not describe the rendering of their site, only the markup of their site, it's up to the user..or it's own browser.. to interpret the markup in a rendering.. by cleverly omitting some divs & moving others somewhere else for instance!)

I don't think it's unreasonable to include, base on the assumption that they exercise it infrequently and with discretion. For instance, they probably wouldn't go after a blind user that uses some sort of auditory interface. Instead, they probably included it for situations like this, as a means to justify their actions.