The real question is how soon will GPT-3(4?) replace commenters on websites like this one, and whether you will even be able to tell.
I'm unsure if it's confirmation bias, but I find myself noticing weird abberations in online comments that don't seem to be ESL related. (edit: it's probably just mobile swipe typing at play)
We'll hardly be able to tell the difference, if at all. Maybe it doesn't matter as long as the conversation is engaging for the human.
And what when people are certain that the machines are better in everything, who will want to chat, listen to music or watch paintings from the "lame" humans, when the robots will be the ultimate solution for every human need?
I imagine it would make it very easy to “seed” a website or a platform with initial “users” and content.
I also imagine it will be (and likely is already) being deployed to create the impression of popular support (or lack thereof) of a politician, business or policy.