The New American Oxford Dictionary defines "advertisement" as "a notice or announcement in a public medium promoting a product, service, or event." By that definition, anything that mentions a product in a neutral light (thereby building brand awareness) or positive light (explicitly promotional) is an ad. The fact that it may not be paid for is irrelevant.

A chatbot tuned to casually drop product references like in this thread would build a huge amount of brand awareness and be worth an incredible amount. A chatbot tuned to be insidiously promotional in a surgically targeted way would be worth even more.

I took a quick look at your comment history. If OpenAI/Anthropic/etc. were paid by JuliaHub/Dan Simmons' publisher/Humble Bundle to make these comments in their chatbots, we would unambiguously call them ads:

https://news.ycombinator.com/item?id=46279782:

   Precisely; today Julia already solves many of those problems.

   It also removes many of Matlab's footguns like `[1,2,3] + [4;5;6]`, or also `diag(rand(m,n))` doing two different things depending on whether m or n are 1.

https://news.ycombinator.com/item?id=46067423:

   I wasn't expecting to read a Hyperion reference in this thread, such a great book.

   > Name a game distribution platform that respects its customers
   Humble Bundle.