All I saw there was BS. Flight feathers on arms which weren't wings yet would serve zero purpose other than getting torn off or damaged as the creature tried to use its arms for grasping or whatever, leaving the creature colder than when he had down feathers in the first place. Natural selection itself would mitigate against it.
How about learning something about evolution and the way it works before you try to critique it? Survival of the fittest does not refer to what *you* think is most fit, but to whatever best enables survival of the species in question. If a feather is such a complicated structure that it couldn't possibly have evolved, then how do you explain that a single-cell zygote without any structure becomes, within weeks, a fully formed bird with feathers?
There were, FYI, several species of feathered dinosaurs besides birds. Here is a nice article, complete with fossil pictures and schematics of many feather types that evolved. It is apparently course literature for an upper level university biology class, but I think it is readable.
You truly think flight feathers could “serve zero purpose” if they weren’t on wings? I find it surprising with how much certainty some of you write about a subject that’s so complex and largely theoretical. This mutation could have emerged first as an exaptation, and through sexual selection become more prominent in the population. Also, it stands to reason that “flight” feathers, before the era of flight, could have still served to provide increased running speed and jump height, assisting the avoidance predators as well as the capture of prey.