Is it normal (or normative) for Polish to retain the original orthography in names? Could it (or should it actually) be 'Dżeka'?
Given that there are obligatory lessons of English in most of the schools, and that people know at least basics of the language, there isn't a big problem with pronoucing English names and writing them phonetically.
Although, there is a habit of using Polish equivalents for historic persons (George Washington is Jerzy Waszyngton, Queen Victoria is Królowa Wiktoria etc), and there is (was?) a law, that names given to children has to have Polish pronounciation, so to avoid people calling a kid for exemple [Yessicka], they are writing it 'Dżesika'. But foreign people's names are always reffered with original spelling.
Jacek (not Jack) is also a Polish name and it's pronounced like "ya-tsek" or something like this.
That's right. And from only one sentence we can't really tell which one is meant. But unless something like "Znasz Jacka Sparrowa?" is added explicitly, I'd pronounce it the way you said, as ['ya.tsek].
Przeczytałem te "Znasz Jacka?" od razu, jak [znash yatska], nawet nie pomyślałem o żadnym Jacku [dżeku] =)
For those who are non-native American English speakers, to not know jack is to know nothing, or to know jack sh*t.