Looks like I'll be sitting down to tea with you over linguistics again, SardonicNihilist. Or is that sitting down to linguistics over tea?
Unlike the different meanings of your "couple" example,
while and
whilst bear no such differences. Both are truly interchangeable, much like
among and
amongst. You can probably thank Chaucer and his fourteenth century pals for these irregularities and adding all things "t" to every other non-noun they came across. Due to such mainly British forms as
burnt and
spoilt, the use, in American English, of all variants ending in
t is considered British and a bit ostentatious. Emerging from the Canadian education system gives you, SardonicNihilist, carte blanche to use the
ts to your heart's content, as well their americanised variants. Personally, I prefer to use the
t variants (whilst, amongst, etc.) more in the heart of a sentence and the non-
t variants at the beginning.
The [couple = few] meaning of
couple seems to be a more modern casual-conversational development.