What I mean the case of Vanitas is written by noe who probably writing it as copy mechanism about vanitas 'death but the comic/noe' s writing is universal narrator.
I don't know this is right term in English but what I mean for universal narrator is when the pov passes between characters allowing the readers knowing all details of story.
Like in lord of the flies. Children believe the lord of flies existw but readers know they confused a paratrooper's body for supernatural being .
Therefore Noé is writing by universal narrator as he manages to collect different povs by people's commentaries of their experiences or their memories.
As consequence the Noe of the memories/manga doesn't know all details of storybut reader/future!Noe narattor know more information and details.
As consequence the small flashback povby other characters can rapresent people who Noe drank on or knowing very well.
I hope I have been more understandable in my explanation.
About Vanitas or couse Noe will drink from him, but outside to have his consent, there are strong implications Luna's memories might be inside vanitas .
Therefore drinking from him might be dangerous, after all Noé suffered by drinking from Misha who was toying with Noe's a sick seek and hide game of memory, or JJ forcing his memories to noé without preparation.
It looks reading blood is a skill Noé needs to power up with experience if your prey refuses to be read or their experiences are so traumatic that you can lose yourself in it.
Vanitas 'blood is a dark soul final game boss, Noe will need a lot preparation for it.
And if i am right about Astolfo and jeanne, their blood are probably dark soul middle boss games.
Astolfo' s blood/Malenia sword of blade of miquella level.
Jeanne' s blood /Lady Maria of the Astral Clocktower.
Vanitas ' bloos level, all the worst bosses together.
