so is 'we feel you're over qualified and would be bored' code for 'please just go away'?

It's code for "We think you're gonna quit this job at the first opportunity."

It's code for we're scared you'll be brainer than us, ask too many questions and make our lives more stressful.

Big companies spend about $1200/employee on training and orientation. Smaller ones spend more than that.

A major concern of HR departments (and something they're rated on) is employee hiring/retention.

A kind metaphor for GTFO

I thought “overqualified” meant “we want to hire someone we can pay less.”

I guess it means "Don't expect an adequate wage."

Usually is

Yep