Every AI needs a prompt. It is easy to master it after playing with prompts on most AI. I do not think those who use AI to reply or create topics are so naive. gptzero according to me still good to detect an AI was used to create a topic or reply.
For me, the best indicator if a post is AI-generated is if it is written in flawless English. Even the best posters who are native English speakers don't necessarily write every post using the precision in punctuation, spelling & grammar executed by ChatGPT. If a user's native language isn't English (as can be evidenced by their posting history), and they suddenly start posting in flawless English, it means one of two things:
I also agree that an AI generated response has flawless English. Still, there are many ways to disguise flawless English if you know how to write a prompt. Even there are a few platforms that can help you with it for free. Even Google is finding is difficult to detect AI written articles.
I would say the best way to recognise if an article is written by an AI is to see whether it uses pronoun and also noun in it. As we humans tend to use it more often for communicating with each other. This where a communication between humans become to and fro.