Hi, Wayne -- on Aug 04 2020 at 21:28, you wrote:

 >>
 >>> I don't think it optional but Nesfield disagrees:
 >>
 >> Speaking of punctuation, I missed a comma before `but'.

WH> Is this comma always required?  If so, who stated and where it is
WH> stated?

It's not always (or even often) required. "But" is a conjunction, not a
conjuctive adverb and therefore the comma should or should not be there
based on context (cf. Fowlers ).

Cheers... Dallas

--- timEd/NT 1.30+