Not the OP and I cannot provide any evidence. However, for a large number of controversial topics, I try to guess the top comment in my head before opening the comments page. My estimate is that 70-80% of the times I guess it right.
That would be evidence that people on the internet are predictable, not evidence of manipulation.
Predictability on the internet, which increases both with group size and with the divisiveness of a topic, is also a huge problem for HN [1]. But it's not the problem we've been discussing in this thread, and I think it's important to make clear distinctions between the issues. It's common for people to leap from some other issue to "astroturfing! shill! spy!" explanations, instead of facing the original issue.
[1] Here's why, if anyone wants an explanation. Predictability is the enemy of curiosity. Worse, when discussions are predictable, there isn't anything intellectually interesting in them, and the mind seems to resort to flamewars to amuse itself in the absence of anything better to do (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...). So predictability destroys community as well.
