I think it depends on what you mean by an Orc treating with a Elf. I took
this as no Orc negotiating with Elves, or having parleys, cease-fires,
amnesties or things like that. I think the situation where an Orc has
been wounded and has an Elf sword at its throat is rather different, and though
many no doubt would fight to the bitter end and never surrender, I think
Tolkien's earlier passages do leave the possibility of surrender for Orcs
open.
As to how you read Tolkien's later writings in regards to the Hobbit, (or even
Lord of the Rings), I think it's more a philosophical point that comes down to
how you view the mythology he created. I think you can look at it
maybe as a series of discreet steps with different levels of connectivity
between the different early and late phases. Alternatively you can
look at it as something Tolkien was developing throughout his life and as
finished up to the point he left it, or maybe even something other people can
add to. These are all valid ways of looking at it, but I go by the middle
one myself, as an expanding vision of Tolkien's, in which case these late notes
could be looked on as retrospectively 'explaining' things left unclear in these
earlier phases. If you go by the first of these though, you then have to
decide how much connection there is between the world of The Hobbit, The
LotR's, The Silmarillion and Tolkien's late essays. After all we can only
really talk of the Elven King as Thranduil father of Legolas, and mention
things like the location of Dorwinion if we have already decided that the world
of The Hobbit is the same world as that of the later versions of the
myths.
