This is causing me much pain and distress!
My commuter bike recently (post HONC) developed a squeak that appeared to be the left hand crank (old sq taper job). After servicing the pedals and removing, cleaning and retorquing the LH crank the creak persisted, so I bit the bullet and replaced the whole lot with a nice fsa gossamer external bb chainset. For the 1st couple of rides it was quiet and sweet – however this morning the damned creak returned! 👿
I've checked the BB shell and can't see any cracks, it's not the saddle / seatpost as it creaks when standing, chainrings are on tight, the cranks are tight and the bb is good.
I've noticed that the RH dropout is a wee bit big, i.e. the axle can shift a bit during a ride, could this be the problem?