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.
I fucking hate these trials they do. They did some bullshit trial with their mobile app not too long ago that turned it into a laggy, unusable mess. Just had to wait until it ended, or download a 3rd party app.
I don’t know what the hell they’re thinking blocking mobile browsers from accessing the site, but they’re seemingly determined to burn through any good-will they’ve got, apparently.