Inconsistencies between list-directed and namelist input

The forms allowed for list-directed and namelist input are similar, but less alike than it would seem to be possible.

Comments are not permitted in list-directed input, but allowed in namelist input.

A character datum in namelist input is required to be enclosed in apostrophes or quotation marks. This is not required in list-directed input if the datum does not contain a blank, comma, semicolon, or slash.

It would be possible to allow comments in list-directed input, and not require delimiters in namelist input of character data under the same conditions as for list-directed input, provided a character datum that begins with an exclamation point is enclosed in apostrophes or quotation marks.

This unification might make it possible to combine discussion of list-directed and namelist input.