Hi Harald,
4. Moderators are encouraged to retain the Message-ID header field
if it is valid, and also retain the Date header field unless it
appears to be stale (72 hours or more in the past)
Charles wanted a SHOULD for retaining message-ID. Nobody else commented.
I also reckon a SHOULD is better for the message-ID. It would prevent duplicates from being posted in case the same proto-article is posted twice (therefore sent to the moderator with the same message-ID). Useful for both auto-moderation bots and manual moderation. And they are encouraged to retain the Date: header (no need for a SHOULD here). -- Julien ÉLIE « La différence entre un chanteur et une paire de chaussures est que le chanteur doit partir avant de lasser. La paire de chaussures, il vaut mieux les laceravant de partir. » (Philippe Geluck)