Have you noticed this trend on HN? Because I see essentially the same sentiment in this thread. Little if anything is effected purely by overt or tacit collusion.
Thankfully HN has a better reputation system in place. News website comments have 0 barrier to entry, and Twitter and Reddit are clearly prone to mass bot'ing. It helps that there's access to an API for transparency on those sites but the persona astroterfing ops are getting more advanced tactics like copying random user comments to build up an appearance nearly indistinguishable from a normal user's history at first glance.
/r/undelete logs many instances of some of the weirdness.
Check any popular political tweet and you'll likely notice the first or top replies are coming from trolls pushing empty narratives.