What an odd question. If the other entity is an AI, there is no need to be polite.

But personally, if I get value out of a conversation, I will continue. If I don't, I'll stop responding. Whether or not the other side is an AI is only relevant if I think I'm building some kind of rapport or friendship with someone. Otherwise what matters is if the comments makes me think, or makes me want to write something. If only AI bots were reading the comments, that would be a bigger issue than if the specific comment I'm replying to is AI-written.

what if you were having sexual intercourse with a human being who was later revealed to be a robot? all the sensations felt identical to you either way. but you still didn't make love.