Below are the full versions of the quotes read or referenced in Episode 6, and their sources.
Then Ilúvatar spoke, and he said: ‘Mighty are the Ainur, and mightiest among them is Melkor; but that he may know, and all the Ainur, that I am Ilúvatar, those things that ye have sung, I will show them forth, that ye may see what ye have done. And thou, Melkor, shalt see that no theme may be played that hath not its uttermost source in me, nor can any alter the music in my despite. For he that attempteth this shall prove but mine instrument in the devising of things more wonderful, which he himself hath not imagined.’
The Silmarillion, Ainulindale
The wedding of his father was not pleasing to Fëanor; and he had no great love for Indis, nor for Fingolfin and Finarfin, her sons. He lived apart from them, exploring the land of Aman, or busying himself with the knowledge and the crafts in which he delighted. In those unhappy things which later came to pass, and in which Fëanor was the leader, many saw the effect of this breach within the house of Finwë, judging that if Finwë had endured his loss and been content with the fathering of his mighty son, the courses of Fëanor would have been otherwise, and great evil might have been prevented; for the sorrow and the strife in the house of Finwë is graven in the memory of the Noldorin Elves. But the children of Indis were great and glorious, and their children also; and if they had not lived the history of the Eldar would have been diminished.
The Silmarillion, Chapter 6, Of Fëanor and the Unchaining of Melkor
But Ilúvatar spoke again and said: ‘Even as I gave being to the thoughts of the Ainur at the beginning of the World, so now I have taken up thy desire and given to it a place therein; but in no other way will I amend thy handiwork, and as thou hast made it, so shall it be. But I will not suffer this: that these should come before the Firstborn of my design, nor that thy impatience should be rewarded. They shall sleep now in the darkness under stone, and shall not come forth until the Firstborn have awakened upon Earth; and until that time thou and they shall wait, though long it seem. But when the time comes I will awaken them, and they shall be to thee as children; and often strife shall arise between thine and mine, the children of my adoption and the children of my choice.’
The Silmarillion, Chapter 2, of Aüle and Yavanna
In summary: I think it must be assumed that ‘talking’ is not necessarily the sign of the possession of a ‘rational soul’ or fea7
The Orcs were beasts of humanized shape (to mock Men and Elves) deliberately perverted / converted into a more close resemblance to Men. Their ‘talking’ was really reeling off ‘records’ set in them by Melkor. Even their rebellious critical words — he knew about them. Melkor taught them speech and as they bred they inherited this; and they had just as much independence as have, say, dogs or horses of their human masters. This talking was largely echoic (cf. parrots). In The Lord of the Rings Sauron is said to have devised a language for Them. The same sort of thing may be said of Huan and the Eagles: they were taught language by the Valar, and raised to a higher level — but they still had no fear.
The History of Middle Earth vol 10: Morgoth’s Ring, p410