[ianai]

Giving your employer the standard two weeks notice is so if they're called by a place you'd like to work for reference they say they'd rehire you. If you go negative anytime during the exit process your management can use that to flip your re-hire status. That's just one way previous employers can affect someone who's left. The balance of power is firmly stacked against the employee and for the employer.

If you want to be a "voice of change" then you'd better have enough evidence to stand up in a court. Anything less can be gaslit.

[kwertyoowiyop]

Also remember, Recruiters and HR move around to different companies a LOT, and they all know each other (BECAUSE they move around a lot!). So you may find that one of these folks at a company you apply to either knows someone involved with your hiring or leaving a previous company, or might have been involved themselves.

[jablan]

Legal circumstances of giving away data of your previous employee aside (which might be very different here in EU), why would my new company rather trust my previous company's bad-mouthing HR than me? And if so, would I be willing to work for such a company?