Earlier quoted context omitted.
We should discourage the use of walled-gardens for public discussion anyway. Otherwise nothing changes ever.
Do you mean closed source software? Because that would rule out Hackernews. But I agree on the principle. Maybe it's the type of discussion. I would be happier if this very exciting superconductor story was unfolding somewhere else than Twitter.
A walled garden is a site that degrades significantly or is unavailable without an account, like Twitter. Anyone can view all of HN modulo dead comments without an account.
You can have a fully open source walled garden.