re: siofra's argument
hmmm... let's look at star wars. admittedly, i don't know a lot of stuff about star wars, but i do have some broad strokes knowledge about how canon is handled. i remember this being a big deal a number of years ago.
is the stuff with ahsoka canon? she's from that clone wars tv show, that takes place between episode 2 and 3. and then now she has a show of her own i guess? but i don't think she's mentioned in any of the movies that take place after that, even the ones that were made after she was a character. but she has apparently been there the whole time, like one of the main character of star wars just had this whole padawan that we just did not know anything about. (the expanded universe stuff that was decanonized after disney bought star wars i would classify as "apocrypha")
i think this is just part of writing stuff in expanded universe, though. seeing a lot of gaps to be filled. hiveswap is, broadly, about the children of jake harley, who is kind of more of a symbol in homestuck than a character. but this is a gap that can be filled, it is not a stretch to assume that jake harley (and the rest of the guardians) had a life outside of the main story of hs. would you feel differently if the homestuck cartoon mentions joey and jude, or uses the more fleshed out version of alternia from hiveswap?
i also think tone is a bad benchmark to use, the tone of hs itself can vary wildly from part to part. we can also take look at another series with a convoluted canon, zelda. is wind waker less canon than twilight princess?
i will say i think canon is a live, shifting thing. for instance, the stuff from the snapchats was just used in bc. if the plot stuff from the end of pq is ever brought up in beyond canon, i would consider it more canonical than apocryphal. even now, i could probably be swayed to include everything that is "officially homestuck" as canon. and of course, the homestuck cartoon will also be canon, even though it is (seemingly) an adaptation of the webcomic.