HB is referring to a "collar bar." The term is derivative of "collar pin," a safety pin employed to bring the two wings of a collar close together, holding them in place much as do the tabs of a tab collared shirt. While the collar pin actually passes through the collar's wings near their leading edges, the collar bar, having front an back halves held together in tension, slides onto the collar's wings. While purists might find the collar bar to be a bit faux for their taste, it does have the advantage of not causing the collar to fray around the holes that result from repeated use of a collar pin. I use both but employ the pin only on shirts of relatively open weave fabric through which the pin can pass without causing damage. There are also shirts, as noted above, with eyelets in the collar to accommodate pins without fraying; too specialized for me.
As Roger notes, the collar bar (or pin, for that matter), passing under the tie knot as it does, gives an arch to the tie that many find attractive. It also anchors collar and tie in place, thus preventing slippage and disarray during the course of the day. To me, wearing both a collar bar/pin and a tie bar is redundant and overkill in terms of metal on the shirt's front, but Astaire was often seen wearing both together, and I sometimes do that too. For that matter, he regularly pinned his button down collars and sometime wore a tie bar with that arrangement as well. That, I have never done, but I'm only 60 and still have time.
Oh, to answer the R.I.P question, no. And GTH (go-to-hell) wide lapels on DB jackets remain the essence of style.