[William Cloud Hicklin]

Giving of rings: let's not forget that the Appendices post-dated the writing of Book I by ten years and more; there is no indication that the story of Thror giving Thrain his Ring while still on his two feet and then toddling off to Moria existed before the writing of Durin's Folk, and almost certainly wasn't yet conceived when Tolkien wrote the passage in question (heck, Moria itself didn't exist yet). At the time, to the extent he thought of it it all, he likely assumed the Ring was handed over on Thror's deathbed, or simply found among the dead king's effects, as it had been from father to son for dwarven generations.

Similarly, the passing around of the Elf-Rings seems to have arisen at the Appendices stage, or at the earliest during the writing of the final chapters in one long burst, and wasn't anything he considered while writing Chapter 2 a decade earlier.