Verses that are repeated in two or more places--but not in all manuscripts--are assumed to be "concordance interpolations" and rejected as spurious by many specialists: at some point, the theory runs, they found their way into some of the manuscripts in the places where they are not fully attested because someone copied them from the places where they are fully attested. Paul explains concordance interpolations as follows:
once there is no obvious ground for mechanical omission (homoeoarchon/homoeoteleuton etc.) AND there is an obvious reason to account for the interpolation, it is likely to be an interpolation, more so of course if it's lacking from several manuscripts. Here, the fact that there seemed to be one verse missing compared to other similar passages would have led to some copyist adding it, either consciously or, especially if he was very well acquainted with the Odyssey, unconsciously. Other such grounds for interpolation are supplying speech introductions to where one was felt missing or if it was felt some clarification was needed.
It strikes me that the urge to condemn and bracket so-called concordance interpolations, exemplified by West and Janko (as well as Apthorp) has to be based on the assumption that, as Paul wrote, "although the pre-Vulgate papyri had a lot of variation, there was a 'core' shared by all manuscripts, more or less identical with our "vulgate", and in addition highly variable, volatile "plus" verses, which were different from text to text."
This is explicitly the view not only of West and Janko, but also of van Thiel. This assumption allows van Thiel to ignore (or at least to not pay much attention to) alternative readings mentioned in the scholia, in ancient quotations, and in papyri; it allows West, and even more so Janko, to condemn suspected concordance interpolations and other material they believe to not to belong to the "core"; and it allows West to "restore" presumed spellings that are not found in any of the manuscripts, ancient or medieval, on the basis of the orthography of eastern Ionian epigraphy of the seventh or sixth centuries BCE.
But apparently the ancient quotations (those before--and some after--150 BCE, when the "vulgate" seems to have emerged) and the pre-150 papyri don't bear out this "optimistic" view (and there is no consensus on whether the Alexandrian scholars were engaging in collating manuscripts or just making things up as they went along--at any rate, Aristarchus' readings often as not didn't make their way into the vulgate). There doesn't seem to be any discernible pre-vulgate "core" Iliad or Odyssey in evidence, as the article on the papyri in A New Companion to Homer notes.
And the "vulgate" itself is by no means uniform, either in the ancient papyri or the medieval manuscripts. Not only that, but no one has ever been able to plot out even a crude representation of the relationships among the medieval manuscripts--and it's highly unlikely that anyone will ever be able to do so. So there is no certainty that a single "vulgate" text that is the ancestor of all the subsequent papyri and medieval manuscripts ever existed.
In these circumstances, it seems to me that there are really no reliable criteria for rejecting lines as concordance interpolations in passages where they are not obviously out of place (as is true of many of these repeated lines). In such cases, there is no way to know whether they were interpolated after the vulgate emerged or before that period (if indeed these verses were interpolated). That these verses are not attested in some of the post-150 papyri or medieval manuscripts may be due to their having been interpolated after the vulgate emerged, but it may just as well due to differences in pre-vulgate texts that were carried over into different papyrus and medieval textual traditions. And if these verses were interpolated before the emergence of the vulgate, there is no real ground for rejecting them, because, pace van Thiel, Janko and West, there's no basis for claiming to be able to reconstruct a "core" pre-vulgate text.