> For me, the whole concept of online forums is interacting with semi-anonymous humans

This is where things break down for me. You want to take humans out of the equation by making any humans that may exist in the process anonymous, to disassociate their involvement, but then worry that the anonymous computer avatars may not be human?

I could at least have a bit more appreciation if you were talking about Facebook Groups, where there is greater effort to make those computer avatars appear human (real names, photos, etc.), but PhysicsForum, HN, and the like chose, seemingly on purpose, to not go in that direction.

If you really want to have discussions with humans, which is valid, why not go outside and meet them where they are found?

> but also the slogan is "science by humans"

If an automotive forum's slogan was "All About Cars" you would disavow any human who uses it? Science by humans can be discussed by non-humans, no? Something and the discussion of something are logically not the same thing.

> Why would anybody make an account on an "expert discussion" site to be misrepresented?

What do you believe is being misrepresented when AI content is posted on a forum? There is no promise of human activity on the typical online forum. To return us to the top, since maybe you've lost sight of what we were talking about, "Using AI to fake posting activity is bad." — but it remains unclear to me why it is bad. I can see how it might end up being low quality "slop", but that is for the users to decide. There is the possibility that users don't find it to be of poor quality and actually enjoy it.