Thanks, guys. I'm relieved, really.
Yep, I learned the need for the handle tie pretty quick.
That was, for once, a good recent addition to the NEC.
A time or two, while working in an old panel, I got zapped by a neutral that I've just disconnected from the busbar, because it carried a current from the other half of the MWBC. No handle tie was to be found on those breakers.
Then again, even for the circuits that weren't meant to be MWBC's, I've come across 'stolen neutrals', used by a completely different circuit. One can only hope that the hot conductors for those two circuits are on different phases...
My recent crazy "old work" find was the jacket of the AC cable used for the neutral.. Lots of crazy folks out there, never know what surprises you'll find. That's why I love our trade.
That, or maybe because I'm new to it