Well, I don't read Sirius/Remus slash much any more, as it's all been done and re-done and then re-done as well, every new fanfic writer reinventing the wheel. I don't even follow the oeuvres of our esteemed ex-Patrician.

And I've only ever written one little fragment of it, on a long train journey with the Nazgul when we went to Strasbourg to go to an Apocalyptica concert, last summer. I had forgotten my book and had nothing else to do, and OotP was still new and fresh in my head.

But I think they are utterly canon. Well anchored in the text. On purpose. Put there by JKR with intent.