When a Polish person has a first name as a last name, do Poles refer to them as his real first name or last name? For example: Marek Witold - isn't it confusing? :)
Also, is it common for such names to appear in Poland?
I'm your example they would say Marek if they knew him well, Pan Marek if they don't know him well. Pan Marek Witold in documentation or in a formal introduction.
But I never really heard Witold as a surname. Polish Christian names tend to form surnames by adding "ski" or "wicz"
-icz typically derived from the Ukrainian / Russian language.
The -wicz ending is Pan-Slavic, rooted in ancient Proto-Slavic meaning "son of."
Its mass presence in Poland is directly due to Ruthenian (Belarusian/Ukrainian) influence during the Polish-Lithuanian Commonwealth, where Polish families, Lipka Tatars, and Jews all adopted it.
Poland's national poet Adam Mickiewicz is a prominent example.
So don't listen to the Saloreich stooge cms_neuf. He is a boomer and doesn't know anything about Poland before World War II and very, very little after that.
It would be interesting to know if they allowed to have both the first and last name the same. Say your last name is Marek and parents want to name their son Marek, resulting in Marek Marek. Do such cases legally exist in Poland?
There is not such a law. The Head of the Civil Registry Office may refuse to register a given name only if it is ridiculous, indecent, in a diminutive form, or fails to distinguish the person's gender. The name Marek is a traditional, linguistically correct male name; therefore, it fully meets all legal requirements.
Say your last name is Marek and parents want to name their son Marek
It's cool to have such a legal name like Marek Marek, but they could ban them to avoid confusion. Otherwise, it would make no sense --- assuming that it's NOT possible to have both the first and the second name the same in Poland? For example, would this name be legally possible:
Janusz Janusz Janusz (assuming that the last name is Janusz and the first and the 2nd names are also Janusz).