"I'd like to move out of my rent-controlled apartment in Spandau because my job is in Eberswalde, but I don't want to walk away from this rate."

That could happen if the Mietendeckel is made permanent and the Abgeordnetenhaus refuses to do its job and adjust it as necessary for a few decades. In reality, your strawman is not realistic.

For every one person in that situation, there are nine who can't move out of their rent-controlled apartment, not because they don't want to walk away from their rate, but because they can't afford to.

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.

> For every one person in that situation, there are nine who can't

I'd be interested to know the actual numbers, but I doubt they happen to be 90%.

When there's more movement in a market, it's easier for supply to increase and prices to stabilize.

Exactly, it's a pain killer. It's about making people shut up and stop talking about the problem.

It's not that simple. Opioids are used all over the world, only in the USA did they cause a crisis. Countries with saner political systems shouldn't judge policies by how they worked in the USA.