The "reply all" function on email is a time bomb, perpetually waiting for someone to accidentally click it at the wrong time.
While "reply all" can be useful when chatting with a small group of friends, or communicating a system change across all company departments, it can backfire majorly when a snarky commented intended for one person gets blasted to an entire email chain.
1. From Greatfreedom:
A design artist at a print shop I worked at ten years ago (I'll call her Z) had always been one of those flakey-but-only-just-good-enough to keep types. She'd create files that looked fine to customers and onscreen, but required sh*t loads of prepress de-f*ckery to make printable. Zero real technical skill, when it should have been half her job.