mmm let's see ... Bulgaria? Krum ? ... Possession ? Would we have a seriously troubled seeker using Ron (over and over) to get the woman he couldn't have at 18 (and taking his revenge on her)?
Author's response
Soooooo - maybe the Bulgarian is just a Red Herring? Interesting note, your point about the unlikelyhood of a schoolboy obsession taken to extremes appears in a later chapter.