I had never noticed this, but after a question in the dfpug forums, I checked the help for ALTER TABLE, and found the following defficiency:
There seems to be
no indication whatsoever that the clauses ADD COLUMN, ALTER COLUMN or DROP COLUMN may be repeated more than once.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)
