Marrettes are definitely a no-no in a control panel. I can just see trying to test a few connections with my meter and hold it at the same time without terminals. The trouble is I've seen it done and it makes me want to cry. Panelbuilding is an art, there is good, and bad, even if it meets code.
As far as using marrettes in a Peckerhead (Motor Termination Box), they work great if you wrap a little tape around them to help resist vibration.
Paul, if you come to Canada, we still spell colour your way. As far as colours go, Canada is pretty basic, our 3 phase is all Red, Black, Blue no matter the voltage, no brown, orange, yellow here. I understand your confusion about all the colours. I had to hook up a gas-fired turbine (Jet Engine) generator in the North West Territories that was Half-Built in Quebec and Finished in Texas and the wiring looked like crayola got a hold of it. Very colorful and confusing at first. (Not as bad as the Russian Motor Starter though....)
Another thing in panels I forgot to mention is to Read the installation instructions for the equipment you are installing. I've seen a lot of PLCs without adequate space for convection cooling as stated in the manual. I guess maybe only the maintenance guys care if it craps out after a year because of inadequate cooling........