Just to round things out, I think there might be (at worst) a Board of Inquiry to determine that the DM was, in fact, rendered useless before being abandoned by the Nautilus.
The board (if you decide to convene it) would lean heavily in the XO's favor because he was the man on the scene (and Starfleet understands and supports its people in the field) and because he avoided a larger diplomatic incident.
Heck, it might be no more than a team from the SCE coming out to interview the officers before going on to examine the wreck (assume the Rillians will allow it or because they have refused to allow an inspection).
One quibble, Tricky- these are the same Romulans who used a weapon of mass destruction on their own Senate and then attempted to deploy it against a Federation world.
There's doggone little loathing for a weapon of mass destruction in the Romulan Empire- provided, of course, that they're holding the trigger.