Ø The PDP-10 had arbitrarily sized byte pointers! Did anybody ever implement a C compiler on that hardware?

I don’t recall a DEC 10 (or PDP-6) C compiler, but such certainly did exist on the UNIVAC 1100 which had a similar arbitrary partial word format.

The Univac never could decide what the character set was, be it ASCII (in 7, 8, or 9 bits) or FIELDDATA (six bits).

I don’t care what they say.
36-bits is here to stay!