Since this review was requested with a very short deadline, it only allows for a "surgical" response.

This draft obsoletes RFC 7234, and Appendix B lists the changes from RFC 7234.  Assuming this list is complete and correct, all of the changes appear to improve the situation from an operational perspective, so it's good to go.

Nit:   == Unused Reference: 'RFC7234' is defined on line 1766, but no explicit reference was found in the text

Thanks to the authors for taking-up this work; several years and many revisions were involved to reach this point.