Take for example Tolkien's statement that only six of the Seven Sons of Feanor ever set foot on Middle-earth.
The passage in question appears in a philological essay, THE SHIBBOLETH OF FEANOR, which is obstinately about a sound-shift in Quenya that got caught up in the power-politics of the day, especially the cult of personality Feanor built up around himself, but wanders off into nomenclature (re. mother-names and father-names).
According to the SHIBBOLETH, when Feanor burned the ships upon arriving in Beleriand, he did not realize that his youngest son had decided to spend the night aboard and consequently burned to death in his sleep. Feanor, demonstrating his increasingly irrational behavior, responds not by any recognition of responsibility or expression of remorse for killing his own son but instead orders that no one ever speak of this to him again.
So we're left with two explanations of this. If this passage represents Tolkien's final thoughts on the topic, then every appearance of Amrod from this point onward in the SILMARILLION narrative shd be altered to remove any mention of Amrod's from them.*
Or, a more interesting but considerably more unsettling option, we can note that the from this point onward in the SILMARILLION narrative the twins always appear together, one never acting without the other inseparably by his side, and conclude that only Amras is actually there, Amrod always accompanying him like an imaginary friend. I like this option best because of its narrative economy, and it certainly underscores the defiance of reality that underlies the whole Noldorian war-on-Morgoth project.
Either way, it demonstrates one of Tolkien's concerns in his latter days: to infuse some of the minor characters in the legendarium with personality.**
--current location: enroute from Boston to Rockford by way of Milwaukee and Harvard
--current reading: THE FAME OF C.S.Lewis by Stephanie L. Derrick (promising)
**another good example being two of Finrod's brothers, Aegnor who is given a little personality late in the development of the legedarium by the addition of a reference to his love for a mortal woman, but not Angrod who is left undefined.