<<"It is best to keep silent ... ." Since every quote that sounds 'Twainian'
is attributed to Mark Twain, is this indeed his? If not, whose?>>

This isn't gonna help much, but don't believe anything that attributes it to
*anyone* unless it cites the specific book/letter/whatever. There's an awful
lot of "definitive" stuff out there which is just someone's opinion of where
a quote originated. If it simply says "Twain" that means "I think it's Twain
(but it might be Lincoln--or maybe it's somebody else)."

Sorry I don't have any real info for you, but I'll do a bit more hunting.

John (ex-Mensa)