I think, however, that there is a misapprehension about the DATE/DATE-
OBS changes. The new ISO date format was very carefully designed to
only be required for post-Y2K data (there was also some overlap
period as I recall). The old format remained - and remains - valid
to describe 20th century data. In fact, the old dd/mm/yy format was
clarified to explicitly denote such dates. No after-the-fact
requirements were leveraged onto archival data.

Plus a that time some change HAD to be made, since the old format
was going to wrap around, while here we have a choice.

1. Keywords that have a value shall not be repeated in a header.

I have many examples (hundreds of thousands?) of files in which
keywords are repeated. Rather than the wording in the current
proposal, I would replace the attempt at a requirement with a strong
recommendation and a clarification that the final copy of any such
repeated keyword should take precedence.

I similarly cannot see the value of this particular proposed
change: FITS readers will need to support repeated keywords forever,
given the very large numbers of existing files with them, so it's
not even as if this would simplify reading FITS. I am also
very much in favour of instead simply clarifying that the last
occurence has precedence.

The other changes look more like matching the letter of the law
with its spirit, so are perfectly fine with me.