As quoted from the linked post.
It looks like you’re part of one of our experiments. The logged-in mobile web experience is currently unavailable for a portion of users. To access the site you can log on via desktop, the mobile apps, or wait for the experiment to conclude.
This is separate from the API issue. This will actually BLOCK you from even viewing reddit on your phone without using the official app.
Archive.org link in case the post is removed.
Why on earth would it be illegal? What possible law could have been broken? You don’t have a “right” to visit reddit with a mobile browser. They have the right to restrict access as they see fit.
A lot of this sort of A/B testing has the character of a psychology experiment. If it were conducted by a reputable research lab, it would have to pass an instituational review board who would weigh in on whether it was an ethical experiment, and among other things research subjects would always have the right to decline to participate in the experiment.
But when private companies do it, nobody holds them to the same standard of ethics in their human experimentation. But clearly people’s right not to be subject to psychological experiments without their consent is being violated.