They'll lower the house prices!!!

[Elmo]

Why were the Noldor who rebelled and went to Middle Earth, when they returned to Aman, were not permitted to return to Tirion? Why were they only permitted to live in a second best Tol Eressëa? Did this show that the Valar did not truly forgive the rebellious Noldor or did not forgive them enough to let them back in to their fair city? Were they scared that letting a large influx of returnees my awaken old tensions between them and the Teleri and Finarfin's Noldor? Tirion must still have been relatively deserted at the end of the First Age so there must of been plenty of space. Did the exiles simply choose not to live in Tirion again because it would reawaken bad memories?

[Galin]

Letter 131 (probably late 1951) states that the Exiles were not permitted to live 'permanently' in Valinor, but in Eressea. However, the version in Quenta Silmarillion reads...

'And when they came into the West the Gnomes for the most part rehabited the Lonely Isle, that looks both West and East; and that land became very fair, and so remains. But some returned even to Valinor, as all were free to do who willed; and there the Gnomes were admitted again to the love of Manwe and the pardon of the Valar; and the Teleri forgave their ancient grief, and the curse was laid to rest.' Quenta Silmarillion HME V

In a very late letter (1971) Tolkien does not speak of the Noldor specifically, but writes: 'The 'immortals' who were permitted to leave Middle-earth and seek Aman -- the undying lands of Valinor and Eressea, an island assigned to the Eldar -- set sail in ships specially made and hallowed for this voyage.'

Anything else on the returning Noldor and Aman specifically? I know there's more about Tol Eressea, but I can't remember right now if Tolkien again specifically states that the Exiled Noldor could not return to Valinor permanently.

If Tolkien, in his letter to Milton Waldman (131), was referring to something he had already written then he was arguably misremembering both the Qenta Noldorinwa and Quenta Silmarillion. If this comment represents a 'revised' idea (being later) JRRT did not, in any case (IIRC) update the passage in question (he seems to have left it untouched even with respect to later 'cursory' comments).