You could check out another instance, for example https://feddit.online/ , which is visible without signing in.
Piefed.social used to be open for all, but I suspect it needed to be restricted due to AI scrapers. Not sure exactly what the reasoning is though.
You can find a list of instances here: https://fedidb.com/software/piefed
There’s no real difference, content flows freely between the two platforms.
I’m writing this in piefed - does it make my comment “piefed content”, while your comment is “Lemmy content”?
The distinction makes no sense. And that’s the point - use whatever platform you prefer, enjoy the same content anywhere you go. There is no “piefed content” or “lemmy content”, only content. :)