Possible answers to these questions essentially revolve around whether one is a follower of the traditional objective Linnean school of taxonomy,like myself, or an adherent of the (subjective, often imprecise and arbitrary) cladistic point of view. Personally, I have no problem in accepting the idea that birds are directly descended from certain theropods. Scientifically speaking,that seems obvious enough. But nothing yet proposed or propounded by the school of cladistics has been able to convince me that these avian descendants of dinosaurs are STILL dinosaurs themselves (which would imply that they still belong to class Reptilia). If this were so, then evolutionary modification toward the production of new classes and orders, significantly different from their predecessors, would not operate. In my opinion, birds derived from theropod forebears are no more theropods themselves than human beings descended from apes are just hairless monkeys.

As for the increasing current trends which claim that most if not all dinosaurs were feathered, and feathered theropod- paravians may have been birds after all (Archaeopteryx, Aurornis, etc.), I cannot find any solid scientific evidence to back up either hypothesis. The tenuous "evidence" of feathers which palaeontologists sometimes discover on dinosaur fossils probably, in most cases, does not indicate true feathers at all, but rather a kind of insulating fuzz or extension of scales. The "early birds" which precede genuine avians such as Iberomesornis and Confuciusornis display an anatomy which is still much closer to that of theropods than to that of birds. Most of these pseudo-birds, although they may have been feathered and winged, were not yet derived sufficiently for flight and did not yet possess many of the distinguishing features of true birds.

I would appreciate polite comments and discussion on these themes.

There is no evidence that most of the dinosaur were feathered. I agree with you " if this were so, then evolutionary modification toward the production of new classes and orders, significantly different from their predecessors, would not operate. In my opinion, birds derived from theropod forebears are no more theropods themselves than human beings descended from apes are just hairless monkeys".
Birds are not classified with reptiles due to their unique features. different hypothesis are proposed but they just end up there due to lack of evidence. So i think better not to be confused.