Some notes on RFC 1464:
As has been noted, RFC 1464 never progressed beyond being experimental, so
calling a TXT record that conforms to it "standards-based" is not correct.
Over the years since 1464 was published I've received occasional inquiries
about it; some people claim to have used it in their applications. However I
believe SPF was the first time wide scale deployment of a 1464-compliant TXT
record scheme was proposed.
The bottom line is that RFC 1464 was a syntax proposal design to simplify
information sharing. A registry was proposed to control name collisions, but
that never happened. It still seems to be a reasonable approach and perhaps
someone will put it back on the standards track someday if appropriate.
Rich
[author, RFC 1464]