Since October 1995 and the publication of RFC 1855.

https://www.rfc-editor.org/rfc/rfc1855

Communication has not been merely a matter of personal habit — it follows commonly accepted standards for exchanging information within a group. Ignoring these conventions risks your message being unread, unheard, or misunderstood.

That said, it seems possible the author is intentionally addressing a specific subgroup that has agreed upon a different set of communication rules.

Status of this Memo: This memo does not specify an Internet standard of any kind. - MY FAVORITE kind of Memo :)