I've posted about this countless times: https://hn.algolia.com/?sort=byDate&prefix=true&page=0&dateR....
There are several ways you might have actual evidence that someone was astroturfing, but they're rare, and overwhelmingly less likely than people just making such accusations up because another user's comment pisses them off. The "you must be a shill" trope is pretty much the most popular internet cheap shot out there, and based on everything we know, it's a far greater threat to this site because it's so common and degrades discussion so quickly. Indeed it's a bit like antivirus software in causing the very problem it claims to combat.
So, unless you have more evidence than someone being wrong in your opinion on the internet, you bet it's inadmissible here.