I agree with the sentiment that this does not imply reddit or hackernews are subject to influence by the United States Government or allies.
I do not agree that the idea is preposterous or laughable. This is because we do know that the NSA infiltrates domestic technical groups as they did with the IETF to affect standards discussions, that they infiltrate activist groups inside the United States to disrupt them, that they are aware of social contagion theory and its usefulness in affecting public opinion, that they have done studies with at least the UCLA on viral messaging for Americans (to compare to, with and against foreign countries), that political campaigns use social targeting techniques without branding and will comment on news articles (to be 'first to post') to color conversation on hot button issues during the races, and that companies with political interests and who share a revolving door with elected office also advertise political discourse online in this way. Thinkst researchers studied how easy it is to manipulate online social conversation, news media outlets and platforms. We know that the GCHQ have JTRIG capabilities to perform internet manipulation and that there are documents from Snowden that specifically mention their use in derailing conversations on online forums. There have been reports of PR firms of private companies astroturfing reddit and others. And we know that HBGary Federal and other cyberoperations contractors for the US Government sell astroturfing services.
What we don't know is that reddit or hackernews are targeted specifically or for domestic purposes by the US Government. We have a few indications that this is done for large media outlets (recently Judith Miller, Ken Dilanian, CNN on Bahrain) in tandem with other leverage like access to officials, exclusive press passes and permission to report at the edges of no-reporting zones. Unfortunately there isn't enough evidence to be conclusive yet about the reddit/HN case as there have not been leaks that speak directly about it, so any debate in this area is bound to be speculation versus speculation.