With the trillion-dollar coin's abortion blessedly assured, Tom Maguire at the Just One Minute blog says "I told ya so." His analysis focusses on the fact that the relevant statute permits only "bullion" and "proof" platinum coins. Both these terms have a specific and well-understood meaning that Congress reasonably relied on in drafting the statute. In sum, the coin envisioned by trillion-dollar coin advocates would be neither a bullion nor a proof coin, as those terms are commonly understood, so it is not authorized by the plain text of the statue.
His analysis is pretty convincing. One could poke some holes in it, but it's enough that it gets us to ambiguity. From there, we can use other interpretative tools to determine the actual intent of the statute, which, after all, it utterly obvious.
This is Part 5 in The Gillette-Torvik Blog's 94-Part Series on the Trillion Dollar Platinum Coin idea.