Do you think you'd have found out and been able to do anything about it if you hadn't gotten that code? Legitimizing censorship is obviously not desirable, but having it masquerade as generic 404's doesn't solve the problem either, it just hides it.
Yes because I really wanted to see that thing. If I get 404 on something I want to see I will try through Tor and I will try with at least a few circuits. And if Tor gets through I then usually test with other networks just as I did with this.
I know that many people probably don't do that and you have a valid point with the masking but a better solution would be stopping censorship, not a new errorcode
But, we can enable Internet companies to better-expose when rights requests and censorship has been used to block information.
Before, all you'd get on GitHub (per the release) was a 403, which could have been any number of things and was, in any case, an obfuscation of why you couldn't access the resource. If a person doesn't see a reason to investigate, they'll just move on.
This gets us closer to conversations about censorship.
If I get a 451 error, I'll know it's censorship and can use something like Tor to get around it.
Actually, I'm sure there will be some browser extensions soon to automatically use a proxy if a 451 error is returned.
This status-code is a great solution to inform the public about it.
It's pretty much the go-to thing for anybody nefarious who wants to have something censored without all the trouble and blatant impossibility of having their claims vindicated in court.
Those obstacles could be censorship, or copyright infringement, or illegal mathematics - anything.