The diner workers are Silas's dogs.
The post-credits scene of The Night Watch has animal growling that sounds very human. Silas has a possible connected to the diner, and the official transcript even says it could be animals or human.The proprietor and server are male and female, respectively. Silas' dogs have male and female nicknames, Don and Molly.
Silas is the woodcutter in the story.
He lives in the woods and uses the same branches-as-directions as the story. Perhaps the people he was 'saving' during the 1896 fire was a sacrifice to the woods. Nora's ghost.
Nora is different from the other ghosts we've seen - she's confined to the observatory, and can recreate the echoes. This is likely connected to whatever is buried underneath the observatory. The ghosts are in Mount Absalom's mineral water.
During the séance in The Sound of Her Voice, Rudy asks his mother where she is. Lulu translates her response as growth/rejuvenation, water, dirt/earth, insect/small (particle?), which Rudy interprets as "under the water pipes, under the ground." But that interpretation only focuses on the middle two notes, ignoring the outer two. A more comprehensive interpretation would suggest something like "we are reborn from the particles in the water."