I agree that what we are seeing are lapels, not simply the inside facing of the coat turned back. The buttons are clearly ornamental, as the jacket would be much too small to be fastened, especially at the bottom. The buttons do seem to be consistent down his right side, on the lapel as well as below it.

Also, I do not think this is a doublet, since there is no indication of a collar at all. We would see it if it had one. What I see, though, is a lapel that is not connected to anything, and it seems to just be flat around the neck, with his shirt collar being the only thing showing.

The length of this jacket also seems a lot shorter than most, which I really like.

Oh, and the epaulets come well past the shoulder seams, which is very different than most civilian versions. On his right shoulder, are we seeing the glare off of some sort of decoration on the epaulet?