@ApatheticAustrian: Sorry, misread your post. Deleted mine.
What should we make of the persistent communists? They're definititely an abheration in the region.
The communists are the barely reformed "incarnation" of the former ruling communist party; some degree of nostalgia continues to exist with certain demographics (mainly the elderly). Eternal opposition does not hurt the party's performance in elections so it seems these people just want to be heard. I imagine it's the same demographic that still votes for Die Linke in East Germany. The communists seem to do best in the northwest (near the German border, in Sudetenland) and in the industrial east.
The Hungarian MSZP were founded in 1989 by the reformist wing of the ruling Communists, and Slovakian Smer's predecessor was founded by communists too, so that leaves Poland as the only country in the region without a party in parliament that has its roots in the communist regime. Perhaps it's just a historical accident that the commies in Czechia continued to stand in elections after communism without reforming?
Isn't the Polish SLD descended in part from the old Communist Party, via the SdrP?
Edit: Forgot they are currently extra-parliamentary. Seems like that is likely temporary, though.