I am curious too. After some research I assume the relevant standard is IPTC 7901, but I don't see a mention of excluded characters in the body of the newswire:

I am curious too. After some research I assume the relevant standard is IPTC 7901, but I don't see a mention of excluded characters in the body of the newswire: https://iptc.org/standards/iptc-7901/ https://iptc.org/standards/iptc-7901/ Perhaps the convention of a limited character set dates back to the telegraph era