This is an interesting thought experiment. I'm surprised the CSS class names are so transparent. They must think they're doing nothing wrong. "Persuation" is about what I'd expect from people who downvote every spelling correction.
The Chrome extension is ultimately an enabler of bad behavior though. I wish someone over on Lawyer News would share a post about how they used their free time to put together a lawsuit against Booking.com for fun.
Also what makes this author think the numbers of rooms left are any more accurate or honest than the rest of the surrounding bullshit? Just the fact that they're numbers? Anyway you don't need that info. Is there at least 1 room (or n rooms if you requested n rooms) left, yes or no? It's a boolean. Available or not.