A lot of it is thanks to the fact that suing people is much less common here, so it never gets challanged. Also the person who lost the case pays the costs here unlike in the US so that's a deterrent.

I've looked into it now and it seems for software the personal copyrights are restricted compared to art. So for example you can't veto changes made to your software after you sold economic rights to it or using it for stuff you disagree with.

> Must I assume that a Polish author can come after me if I follow the letter of CC-BY-SA-3.0, but not in a way that he or she likes?

I think they'd have to prove that the way it's used harms them. It's not enough to say "I don't like it". But again IANAL.

There has been some cases for example about using Solidarity movement logo from 80s by various now-conflicted post-solidarity political parties and their supporters. I don't know who won, but I know that the author of the original logo was involved despite giving the rights to that logo to anti-communist opposition decades ago.