[KyleGoetz]

chryuop I'm not sure what you're getting at. Are you saying that だの (だ preceeding の like you said) must become だな? That doesn't make any sense.

And note that 学生なのだ and 学生のだ are completely different constructions. The former means "He/she/it is a student," while the latter means "It is the student's [thing]."