About Lupin's boggart

[pippin_999]

No: HPFGUIDX 129935

Many people have asked why there should be any doubt
about the identity of Lupin's boggart.

I would consider it solved, except that in OOP it's still being
called a silvery orb
---
Lupin looked from Mrs. Weasley to the dead Harry on the 
floor and seemed to understand in an instant. Pulling 
out his own wand, he said, very firmly and clearly,
"Riddikulus!"

Harry's body vanished. A silvery orb hung in the air over 
the spot where it had lain. Lupin waved his wand once
more and the orb vanished in a puff of smoke.-- OOP ch 9
----
The narrative voice is not given to poesy --  so why not
say 'moon'?
  
The other point is that Lupin doesn't say straight out 
that his boggart is the full moon -- he uses the same 
sort of equivocal language as when Snape asked 
about the map.

"Full of Dark Magic?" he repeated mildly. "Do you really
think so, Severus? It looks to me as though it is merely
a piece of parchment that insults anybody who reads
it. Childish, but surely not dangerous? I imagine Harry
got it from a joke shop--" PoA ch 14

"Or did you realize that the boggart changed into the 
moon when it saw me?" -- PoA ch19

Pippin