Christopher,
The Cumaean might be addressing the White Fountain in a metaphoric manner, but on the surface the real star she is talking about is the Fish's Mouth, aka Fomalhaut (or "Formalhaut" for epopts of the typos--you know who you are). The target of their ftl (faster than light) telephone call attempt; once again, unobstructed line of sight is required.
Nutria,
You are raising most of the points about posthistory that I raised in "Additions, Errata, &cetera: volume 2," which I applaud. Now all that remains is for you to whip up the timeline that you believe strongly enough to take the whipping for! Go to! Look forward to seeing it!
=mantis=