It's hardcoded in the PieFed source code, so every instance does this by default unless you patch it like I did.
The combined swearwords + excluded communities list seems to appear at least 3 times in the codebase (not referenced, copied verbatim).
Let's just say that it wouldn't pass my code review if I saw this at work
EDIT: It has been removed from 2/3 places in the codebase.