I think it is unfair to TDT to say that it is just Hofstadter's superrationality. If TDT is an actual algorithm to which Hofstadter's argument applies, even just in the purely symmetric version, that is a great advance. I would definitely say that about UDT.

Yes, TDT is underspecified. But is it a class of fully specified algorithms, all of which cooperate with pure clones, or is it not clear if there is any way of specifying which logical counterfactuals it can consider?

Two relevant links: Gary Drescher on a problem with (a specification of?) TDT; you on underspecification.