@yesiam_a_pirate Let me reflect on my radio broadcast engineering days: If our studios (and offices) were co-located at a transmitter site, with a broadcast tower (i.e., a giant lightning rod in the sky) on the property; we mainly grounded audio equipment and broadcast equipment to reduce or eliminate lightning damage. 99% of the time this also helped in reducing hum when connecting numerous studios full of audio equipment together with each other. Many times broadcast audio equipment also had *this* grounding lug on the rear chasis panel. Now if you had a professionally built broadcast facility; you typically had a 3" copper ground strap running between all studios; which terminated at the broadcast tower's ground system (or if you didn't have a co-located transmitter or tower, the ground was tied to the building's star ground system). When that 3" ground strap was available, each equipment chasis ground lug was tied to this ground strap (along with plugging the 3 prong AC plug in the wall for power). If lightning struck the tower, this ground strap provided an extremely low impedance ground, but more importantly it kept all equipment connected to it at the same low impedance ground potential. I still employ much of what I learned and used at broadcast facilities on my home audio and grounding system. The result is extremely low noise floors.
To lift or not lift the pin 1 connection on an analog XLR connector is another topic related to grounding. In a broadcast facility it's almost impossible to control this issue with sometimes hundreds of XLR connections taking place (in the good ol' analog days), but since most radio stations had decent star ground systems incorporated, this most times wasn't a problem. Now almost all radio stations are wired digitally, eliminating a lot of ground loop problems. Again, this same scheme can be incorporated into home audio systems with numerous pieces of balanced analog gear interconnected. IMO it's much easier to control this in a home environment as compared to a radio station environment. Learning how to solder can be a very important skill to know when setting up a home audio system, as you'll want to be able to unsolder or solder, some of these pin 1 XLR connections when hum presents itself.