OutsideObserver <Stand And
wrote...
....
IF you subsequently edit the hyperlink in any way, the formatting gets
reset to the STUPID MS default, which should ALSO be something that we
can set down as OUR standard defaults.

You need to change the Hyperlink and Followed Hyperlink styles.
Excel's behavior is poorly documented, and it might not be ideal, but
it's not a bug. This does mean you can't use different hyperlink
formatting in the same workbook. Again, maybe not ideal, but not a
bug.

Another one is the validation comments. *They too should be something
the workbook author can set, and the default setting should also be able
to be modified.
....

?

Do you mean Data Validation input and error messages? They're set,
respectively, in the Input Message and Error Alert tabs of the Data
Validation dialog. They can be set specific to each cell for which
data validation is applied.