The difference is that Rust doesn't gate comments on proof-of-use, even if core contributors might find it annoying. Honestly, this is the first I've heard of such a policy in a project (though no doubt it exists elsewhere, in the infinite span of F/OSS projects).

This isn't to say Zig's stance is unreasonable, it may even be sensible. But you cannot state that people are "welcome to engage and debate the idea on its merits" when that clearly isn't the case. Some people may be welcome to do that; even if there is a strong technical argument or important questions being posed, you are explicitly not welcome unless you meet that criteria, as evidenced by real comments being deleted from that issue.