"""
Be conservative in what you do, be liberal in what you accept from others (often reworded as "Be conservative in what you send, be liberal in what you accept").
"""
Didn't we decide later that that's a bad idea? I mean, in the early days of the web, Internet Explorer was the very embodiment of this principle and a couple of decades later the internet is still full of the resulting non-standard crud.
Yes we did. It can also lead to really surprising security issues in protocol-land where such "liberalism" interacts badly with security-sensitive portions of protocols.
(Security is non-trivial and mostly there are very good reasons that things are exactly as they are in such protocols.)
