[johnisgood]

It is very easy to filter those out from the output of GPT, though, using basic UNIX utilities. In fact, many methods don't survive reformatting or copy-pasting, not requiring filtering at all.

It is a very basic watermark technique (text steganography) if it indeed is supposed to be one.

A more advanced one would be a linguistic (grammar-based) one, but I am not going to give any more ideas. :D

[rep_lodsb]

It's easy to remove those characters, but that still requires being aware of them, and an intent to deceive. So many people just copy LLM output here because they (wrongly) believe it adds something of value to a discussion.

[johnisgood]

I do not think either that pasting output of LLM typically adds anything to the conversation. It might, usually it does not.