[hannob]

This is ultimately an application of the "robustness principle" or Poestel's law, which was how people build stuff in the early Internet.

Plenty of people believe these days that this was never a wise guideline to begin with (see https://www.ietf.org/archive/id/draft-iab-protocol-maintenan... which unfortunately never made it to an RFC). However, one of the problems is that once you started accepting misconfigurations, it's hard to change your defaults.

[ekr____]

It actually did end up as RFC 9413, albeit somewhat softened.

https://datatracker.ietf.org/doc/rfc9413/