Seems like a purely anti-competitive move considering that Reddit is owned by Conde Nast and most of those sites blocked are direct competitors to Conde Naste's publications. Conflict of interest.
Not sure how to feel about this, on the one hand if they were cheating then blocking them makes sense, on the other hand, I don't see a public list, and this could be abused by admins to block unfavorable sources (maybe not the current admins, but who knows what batch of admins we'll get in the future?)
This is interesting to me as someone who works for a subsidiary of a parent company, suffice to say we are very, very much in competition with a number of the other subsidiaries. This in turn is how the parent company benefits, by getting a slice from all of us. Not saying that's necessarily happening here, but figured worth pointing out.