"B A R R Y" wrote in message ...
AFAIK, there is no separate "certification" for an airplane for IFR,
over 10,000 ft., or night flight, as long as the aircraft meets the
standards stated in Part 91.

Assuming you mean LSAs:
My understanding of the "rules" are that the LSA must be operated within the
limits of the manufacturer's operating manual. The manufactuer does not need
to "grant" privilages, but if it prohibits operations then that's the end.
Also if any component installed by the manufacturer prohibits IFR ops then
the manufacturer must accept that under the ASTM guidelines and thereby
limit the LSA to non IFR. Naturally the FAR part 91 minimum equipment rules
still apply.