Quote:
Originally Posted by BenBullock
I'll stick my neck out and say that I don't think there are any exceptions.  |
True but the more important truth is that native speakers don't use だ as a neutral sentence-ender that the OP appears to have been taught to use.
I (a native speaker) would have to be fairly irritated or unusually determined to write something to ever say 書いているんだ or 書いてんだ. At least the OP should know that he will look more than goofy if he finishes every single sentence (or even one out of every 4) with だ.