For me, OTP means a "pairing I especially like to ship." Mine would include Remus/Sirius, Merry/Pippin, Percy/Oliver, Harry/Ron, Horatio/Archie, Will/Bran, and Nicholas/Smike. (There's a definite trend in that list.) But I read other pairings, including these characters with different partners. I don't get upset when I see fics that break up these ships.

Though with Remus/Sirius & Merry/Pippin, I don't think any fic author could convince me that these characters don't love each other. So I could enjoy a Sirius/Snape story, but not if Sirius was characterized as completely uninterested in Remus.