As the one who perpetrated the phrase that has created such vigorous discussion,
let me begin by saying that although I have spoken English for most of my
life (even attended and matriculated (O level GCE from Cambridge) from
what is called an English-medium school in India), I am not a native speaker
of English, and the language that I speak and write is a mishmash of American
and British English with a few phrases from Indglish thrown in.
@callithumpian's suggestion "...the original comment was an accidental mash-up of these two..." is dead on target: I mashed up two intensifiers, perhaps accidentally, but more likely because of a failure to do a final
proof-reading after editing my comment to fit the length constraint
imposed by stackexchange (I deleted a lot of extraneous stuff).
The "Please, pretty please, with sugar" and the
elided "on top" is from my life in the US and
I learned to use it while wheedling my children and
grandchildren and their friends. The "knobs on"
definitely from my reading during my schooldays
(fifty years ago!) which was almost
exclusively of British authors with the exception of Mark Twain.
I might be remembering the phrase from a P. G. Wodehouse novel or
story or even from a Billy Bunter story. I have always understood "with knobs
on" as meaning embellishment or adornment and not as referring to knobs
(or gobs) of butter. I wanted to make my plea to OP Tim to ignore
certain pieces of paper more emphatic, and mixed up two phrases
in my hurry to do so:
knobs on certainly does not seem applicable to sugar -- on top
I think it is the first time that something I have written has
led to a top-ranked hit on Google. Oh, that any of my
intentional writings were so fortunate!