it was acceptable in 2024? what year did it become unacceptable?

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.

Unclear, but it looks to be somewhere around the year 1000.