Yeah what many of those links can be summarized with is this: Because someone has found a piece of an ERV insertion with a function (such as a transcription factor binding somewhere within an ERV insertion), then all ERV’s (and the rest of the ERV where a transcription factor binds) are functional.
But of course, that doesn’t follow and no good evidence supports it. One does have to wonder, though, just why it is so many putative important organismal functions have to be implemented by mutationally decaying remnants of the well-known viral genes GAG, POL, and ENV.
God: “Hmm so I need to express this gene over here in this particular tissue, how to make this work? Ahh of course, let’s use another copy of a viral reverse transcriptase gene for that, for the thirtyseventhousandth time, looking exactly like it’s been accumulating mutations under prototypical transition bias.”
Go figure.