I don't understand other people's brains.
For the most part, I think I do pretty well; after all, as a fiction writer I regularly practice putting myself in different characters' headspaces, actively working to expand my empathy. But I'll admit that I still fall prey to the human tendency to believe everyone else basically thinks like I do at the core, just with different likes, dislikes and preferences. Then every once in a while, I get a sharp reminder that it's not true.
Take the case of the social media comment called to my attention this week. I won't go into great detail, but the thrust of the point (aside from some juvenile name-calling and derailment) was that in this fan's opinion, Capaldi wasn't worthy of the mantle of Doctor, and therefore didn't "count" in their mind.
Usually I'm glad to agree that there's no such thing as canon in the Whoniverse. Even within the thirty-four televised seasons, there are so many self-contradictory ideas that each fan pretty much has to decide for themselves what they want to believe when an inconsistency crops up.
Then there are the media that spanned The Wilderness Years: novels and audios and comics, each with their own cast of regular characters, key in-universe events, and die-hard fans. When no one thought the show would ever return to television, the franchise understandably took a new direction, and a great many fans went along for the ride. Who is to say the stories they hold near and dear can't be canon?