Snape eating or not eating

[Kirstini]

No: HPFGUIDX 68631

<Snip lots of reasons why Snape is never seen eating at Grimmauld 
Place: Vampiracy, Suspiscion, Pureblood conventions, Florence in a 
flowery pinny holding Little Sev, eating with his dear old mum 
instead>

I think that someone proposed another reason when this topic came up 
immediatly post-OoP, concerning warrior culture. The theory was that 
Snape wouldn't eat/accept hospitality at the house of his enemy, 
because that would put him in said enemy's debt. Another one 
suggests itself to me too: he simply didn't like the company. The 
only person we see him having any sort of interaction which could 
possibly be construed as friendly with at all is McGonagall, and she 
only made one visit to Grimmauld Place over the summer (evidence for 
a possible Mr McGonagall? I do hope he's called William). It would 
be very difficult for Snape to maintain his strange and not-terribly-
wonderful relationship (for whatever reason it exists) with HRH 
after crushing a cup of wine with them. 

Kirstini