Ok,

Since I originally asked the above question:
The desirability of platinum plugs, generally, is that they wear out at a
slower rate, hence their gap increases less for equivalent mileage,
(therefore giving a more consistent spark). Given the proper part number of
the plug selected for the particular application, there will be a negligible
increase in current rise in the coil over the secondary windings when the
primary windings are opened by the (points, hall sender, Morse code sender
key etc.) compared to a conventional plug.

I have seen the triple electrode plugs wear the normally round center
electrode to a triangle shape, increasing the gap to .040" and beyond, which
will certainly require more current flow for the same combustion chamber
pressure as a plug gapped to, say .028". This wide gap will not "kill" a
coil, but will result in some drivability problems, depending on the state
of health of the engine in question.

Platinum plugs have been used in both racing and aviation applications for
decades, and racing aside, and from my personal observation, no change in an
aircrafts magneto system has ever been required by an engine manufacturer
because the owner elected to go from massive electrode plugs to platinum
tipped. (the big reason a lot of private aircraft owners don't use platinum
is $$ per plug, sticker shock). Platinum will usually outlast a conventional
plug 1/3 again as long, sometimes more.

Successfully using 'p-tipped plugs for 6 years, same coil on the '87
Vanagon.

Dave Milo