You didn't say, but I reckon this is a survey of
man(7) macros that
might be considered extensions?
My presentation was too cute for my own good. I pointed out the
consistency of xS/xE for various x. I apologized for EX/EE, which
varied from that form (as UR/UE did more recently), and I
questioned OQ/CQ, which utterly breaks it.
The intended point was that one should have a strong rationale
for deviating from established custom, and thereby fostering
mental overload.
Doug