This idea applies to real people as well since there's a different version that exists inside of everybody's head that's seperate from the "real" version. It's just a hypothetical, philosophical thing. There's only practical application of this with fictional characters.

If I believe in Jesus Christ I would not get mad if someone else believes in him, but probably will befriend him (considering all sectary violence in the history of christianism this is an awful example, actually).
Same with 2D characters. Our love is unidirectional and those characters aren't limited by time or physicality.
I think being jealous in this cases only happens because someone is trying to copy 3DPD mechanisms into 2D (because they wish to be like one of them?). In 3DPD "love" means posession and exclusivity, mostly because men wants to spread their genes only and not end caring of someone else progeny without knowing it and women need a stable provider.
So applying this biological motivated behavior into 2D is, at the end, nothing more than irrational. Same with gay marriage, for example.

Personally, I wouldn't really mind either. My Kisaragi =/= someone else's Kisaragi.

>>21482
Like >>21483 said, everyone has their own personal interpretation of fictional and real people. However most of the time there is enough common canon ground to consider all these interpretations a single character/person. However Vocaloids take it a step further, and there is no canon, or rather whatever you believe fits most is the canon.
I can completely relate to what Kondo is saying here. As I met Miku and kept listening to her songs I formed my own interpretation of her character based on the songs I listened to. The interpretation I eventually fell in love with. But when I interact with other people who are in love her, I can see that they have completely different interpretation of her. My Miku might be a cute, sweet dandere, but there is that guy with tomboy Miku or mature idol super start Miku. I just can't feel jealous towards them because it's like different character, there is no "plane" on which we could compete. I found that pretty much every Mikufag thinks this way, but I guess this is the result of specific Miku's nature. I think it's natural to get jealous over sharing your waifu under other circumstances.