The Silmarils and the Rings

[Mithadan]

While the Concerning... The Hoard discussion continues regarding whether that note represents, in whole or in part, a final conception of The Fall of Doriath and The Wanderings of Hurin, (for the full text and that discussion, see http://forum.barrowdowns.com/showthread.php?t=19607), a couple of lines at the end of that document have caught my attention. Tolkien writes:

The Silmarils had become to Feanor symbols and instruments of power: he called himself “the lord of the lights”. The Rings began in that evil mode in which the Jewels ended.

Ignoring the question of whether it is stated elsewhere that Feanor referred to himself as "the lord of the lights" (he seems to have said something like this, but not speaking in the first person), what does Tolkien mean by his comparison of the Rings to the Silmarils?