The closest thing I can think of is the "Star Chamber," a branch of the Tir Tairngire government. Possibly a reference?
Elves that they are not:
* Leonardo. Goes by Brightlight.
* Aina/Alachia. One of them goes by Hecate, I am unsure which. Neither of them seem the sharing type, and Aina is dead. Maybe. (Was the Better than Bad thing canon?)
* Lady Brane. Too young.
* Jane Foster. Too young, goes by Frosty. She's the most likely to share info, but I doubt that Harlequin would tell her anything useful. In any case, it'd make more sense for her to post as Frosty if this were the case, since she already has a presence on Jackpoint.
* Jenna Ni'Fairra. Too young.
Elves they could be, but based on personality I doubt it:
* Aithne Oakforest
* Lugh Surehand
* Urdli
Elves that might be:
* Unnamed newcomer
Non-immortal elf possibilities (Mostly WMG and nonsense):
* Garlthik One-Eye. Supposedly a long-lived ork, possibly immortal. I suspect dragons, not "steals a day back from death" or w/ever every night. Highly unlikely due to SR/ED split.
* Immortal Human. There is some precedent w/ Black Lodge lore, but unlikely- the oldest "immortal humans" were only around 400-500 years old. Unlikely due to SR/ED split.
* Dragon. They aren't the sharing type, but they aren't above posing as other metatypes. Highly unlikely.
Edit: Ack! Forgot the actual Stardust entry. He's almost assuredly a "newcomer:"
Stardust fooled them all
Hiding from nÓg and Tairngire
This indicates that Stardust has not interacted with either elven nation.
And the motley-faced fool
Played dead back in ’16
Sixty-four years hence
He has a distinctive appearance (Motley-face). He faked his death shortly after the awakening (Explaining why he hasn't appeared in any books).
He played with others then,
Now he just wants to break the rules
Once he made love with Gaia,
Mr. Jones tried to heal us all
But the elders weren’t worthy
So he cursed their souls away
And now he’ll make them all pay
Assuming "Gaia" is Earth, this elf used to love nature. "Mr. Jones" might be a Johnson from Drawing Destiny who used the same name. I haven't read the book yet, so I can't say for sure what "healing" Mr. Jones might've done. Either way, Motley decided he no longer liked the "elders." This could refer to dragons, immortal elves, all of the above, or maybe just a sect of them. Because he "made love" with the Earth, presumably this means it is no longer the case. Speculation, but perhaps Stardust is a toxic shaman? That's not pretty for an immortal elf.
I don't know if "curse" means verbal curse or magical.
Motley’s really gone,
Stardust isn't the same person anymore ("motley-faced"
and the scribus is dour
The writing is set in stone (The writing's on the wall, in other words)
They wasted the time,
the days and the hours
Nothing is sacred,
No, no not any more
Settled will be the score.
Straightforward
DRJ
No idea who this is. It could be Stardust's initials, but just as likely it is not.