@stef
Looking at the message board it seems to be:
孤高の名無し吸血鬼: ID.misORE
血の代わりにトマトジュースとか正気か?
作者はもっと調べて吸血鬼描けよ
孤高の名無し吸血鬼: ID.RinSAma
人間風情が吸血鬼の何を知っている
知った風な口をきくなニワカ
I'm not proficient enough in japanese to understand the subtle details but someone who's totally not mizore is basically asking "Drinking tomato juice instead of blood, are you crazy? The OP should investigate vampires more." (not sure what 描けよ actually implies here though)
Rin is basically answering back "What do human (nature) know about vampires? Don't listen to this guy who's just acting like he knows shit" (ニワカ here is a mystery though. Only thing I'm getting on it is 俄 which just means "sudden." Might me some kind of message board slang?)
Disclaimer: I do not actually know japanese