Giving people "incentive to move" – aka forcing them out of their homes – doesn't increase supply. Unless they're "moving" onto the streets in which case you did free up a flat.
Well-off-techies who somehow stumbled into both getting a grandfathered rent controlled rate, and a job in the next city over might be a majority of posters on HN[1], but are a tiny minority of the population. You probably shouldn't be basing overall public policy around them.
[1] I personally think it's unlikely.
I'd be interested to know the actual numbers, but I doubt they happen to be 90%.
Even if there was rent control both places, you'd have to find a rent controlled apartment in the new place. And in reality, you can't, because nobody is willing to leave their rent controlled apartments in the next place either.
They aren't theirs. They're renters.
First-world jurisdictions (including all 50 US states) universally recognize that eviction is a big deal, and that it is not equivalent to forfeiting any old rented property. Accordingly, landlords cannot do whatever they please just because they own four walls, a floor and a roof.
Of all the things you could nit-pick, I can't even begin to understand why you would choose this. Your point is not only pedantic and cringe-inducing, it also betrays callousness beyond that of even American courts. This is truly an accomplishment. Bravo.
By renting you’re in a (heavily regulated) business relationship with an owner, and they own the property. Growing overly attached to something that you don’t own, and calling it yours is risky. I know that tons of people don’t have luxury of owning their places, but that’s how our capitalism world works - ownership is king.
A purpose built apartment building owned by a property company (of which there are many in European towns/cities) can easily be a home for large part of person (or families) life. There are also fairly strong renters rights in many European countries, unless the tenant wants to move they don't have to.
Renting a converted property or whole house from a small landlord could mean they decide they want it back with short notice, at least that is the situation in the UK. Assuming that will be a home long term is a bad idea.