I read the whole thread, and the developers don't come off as principled, it feels more like they're just wedded to a particular implementation and are grasping

I read the whole thread, and the developers don't come off as principled, it feels more like they're just wedded to a particular implementation and are grasping at all straws to defend it. A singular regular expression as a slur filter is pretty terrible by any modern coding standard. I'd avoid the project on the grounds that the rest of their code is probably just as amateurish.