The only difference to the original was my profile picture, which was an explicit porn image.

For several weeks everyone searching for my name or my StackOverflow answers saw that. I'm glad that I was not looking for a job at the time.

I exhausted all possibilities on all channels to rectify this situation short of using a lawyer. I put a lot of effort into getting things in order and seriously considered going the legal route but ultimately decided against it mainly because courts are hit and miss here when it comes to reputation damage of regular individuals as opposed to companies or celebrities.

EDIT: I should have answered your question how this is Hetzner's fault more directly. The website they were hosting did not have the (in Germany) mandatory legal notice (Impressum) or any contact details. This shifts the responsibility to the provider (Providerhaftung). Also I would like to note that I did neither request them to give me their customer's details nor to shut down the site. All I wanted was them to work with their customer to have the offending image removed.

Also I am convinced the porn image was not malice but an accident. The scraper replaced all profile images with ones they probably scraped from a forum. I was just unlucky to get a very indecent one. Had Hetzner collaborated I'm pretty sure this could have been resolved in no time.