Almost every window has scratches - what is considered normal?

Because we were the direct clients, we were able to withhold the payment until everything was resolved.

Whether and how the information sheets are binding or contestable, I unfortunately do not know either. It would certainly be interesting. So far, I also have not had an appointment with the window manufacturer to discuss the errors. To address your mentioned IT area: With TFT displays, a certain number of (sub)pixel defects are also permissible and there is no right to exchange. But there is even ISO 9241-307 with different classes.

Nice that you bring up the example with the TFT. I have thought about that too. And precisely that is one of the sticking points for me. If I have a cheap monitor for 80€, I accept that. If I have the professional variant from Eizo, then not. And we don’t have a DIY store window here either, but the expensive one from the specialist dealer from Internorm.

Here it is such that the top Eizo monitor from Techn-Nikkk was scraped against the loading edge of the truck, so now there are scratches on the casing. Something like that then goes somewhere as B-grade goods at a reduced price over the counter.

(An der Stelle kann man gleich mal eine Notiz für die Umzugsplanung machen ).

With TFT displays, there is the ISO standard that specifies how many defects are permissible in each respective class. Unfortunately, I do not know if there are precisely defined classes for windows. But maybe someone with expertise in this area will be found. Otherwise, it is unfortunately mostly speculative.

Because we were the direct clients, we were able to withhold payment until everything was remedied.

that is actually the only proper way. simply do not pay as long as the work does not correspond to what is contractually agreed. whoever wants something must also sue. the company wants your money, so they will sue. you then counter with the faulty execution and the lack of defect remediation (document this!). demand that they pick up the work again. the windows are great for free after all. if you want money as compensation, you won't be happy with that. polishing is, however, a common reasonable procedure. it’s not as if the windows are polished every year or anything like that.

With us, the defects are not as severe as with you, but the scratches also bother us and we wonder how we should behave. It's simply annoying, even if it's not a huge deal.