Is there some Lemmy rule somewhere that I don’t know about that says I can’t attach a Creative Commons license to my comments?
It’s pretty much just a flag in the robots.txt
Because everyone knows that’s always honored and obeyed, right?
Also, it’s a proprietary flag created by Google and only used by Google (per the article you linked).
So if you want to actually make a difference, lobby your Lemmy instance to add this flag.
Or do both.
Because users are the final owners of their own content, their own comments. Not Lemmy, not anyone else. They have the first responsibility of protecting their rights.