If the universe is compact then there is a twin paradox that is resolvable only by selecting a preferred inertial reference frame (arXiv). I was under the impression that the lack of a preferred inertial reference frame was an empirical result (e.g. from early experiments designed to measure Earth's movement against the aether).
But if I've understood these first points correctly then we should not still be entertaining the notion of a compact universe at all, as in the top voted answer to this question.
So: Is a compact universe theory still viable? If so, what might account for the lack of evidence supporting a preferred inertial reference frame (or is there actually now evidence of a preferred frame)?