As you know, some servers use redundant power supplies; they advise putting the two power supplies on independent circuits so a breaker trip won't down the server.
Common North American 120V receptacles have 2 sockets on them (called "duplex receptacles")... and they can be split and fed from 2 separate circuits (each with their own neutral; not an MWBC, though that too).
I have heard a rather interesting claim over on our DIY forum that HP once (10+ year ago) had installation instructions that said to "split" a duplex receptacle and use each half for an independent circuit.
I have my doubts about that, since a) why would they care?... and b) it's a NEC violation.
It's technically legal to feed 2 circuits to one recep, but the circuit breakers must be handle-tied to protect a future maintainer. Handle-ties tend to cause common trip, which defeats the purpose!
Does anyone have any recollection of such an instruction existing in HP or other server's installation manuals? This might have been perhaps 10-15 years ago.