My first initial reaction to ChatGPT was that people will join more and more verified private human communities. Example: Discord channels or private Whatsapp groups.
My second reaction was that the internet will need a protocol to verify that the user is indeed a human.
Maybe it's simple embellishment, but maybe in some cases it'll be a non-native speaker using an LLM as a personal translator as a way to participate and fit into previously-inaccessible communities. Either way, even with current tools it won't be hard to evade detection; In your example they simply used an inadequate prompt or model.
Definitely in two years it'll be a breeze just to give an LLM instruction on how "you" would chat and set it loose on a chat server without most people noticing.
Discord messages are usually pretty short so it wouldn't need a super-long context either.
It's already extremely difficult to filter out unwanted content with easy to spot identifiers. Almost all social media websites have this built into their designs.
My second reaction was that the internet will need a protocol to verify that the user is indeed a human.