Expecting employees to stick around when they find out they're 20% behind peers is also ludicrous.

I can't imagine the majority of managers fixing it and I can't imagine an employee doing anything other than finding a new job. Everyone loses this one.

He was expecting to be paid the same as his colleagues and the industry standard. That sounds like a fair expectation, irrespective of the percentage raise that implied.

Then he shouldn't have taken the low offer to begin with. That's on him at least as much as the employer. He's free to leave of course, but complaining about it after the fact?

I don't feel complaining about being paid under market rate is a strange thing. 20% raises are not ludicrous in any way, if this prevents an employee from leaving.

I didn't say he should have stayed, he did the right thing, but going in at x and expecting x+20% in six months is ridiculous. If he was expecting that then he should have got that pecific number negotiated up front.

The company has more information than the candidate when making salary offers. If they negotiate in bad faith, that burns up goodwill. It's their decision to do it! I've never heard someone ask if their salary is in-line with the other members of their team (adjusted for performance/experience): it's a given assumption that _the company isn't going to pay you massively less than your peers_.

Plenty of companies do, because HR does the negotiations & their motivation is to minimise employee costs. If you're not negotiating with the recruiter/hiring manager, you're likely to get a poor offer.