Well, for one thing, it seems like the AI did that autonomously. Regardless, the author of the message said that it was for others - it's not like it was a DM, this was a public message.
> Why should anyone put any more effort into a response than what it took to generate?
For all of the reasons I've brought up already. If your goal is to convince someone of a position then the effort you put in isn't tightly coupled to the effort that your interlocutor put sin.