this is a tough one because the way i feel is primarily that it describes a relationship of power over the text. like, it's kind of cringe to talk about "biblical canon" when "fandom canon" comes up but i think it's genuinely pretty useful sometimes.

like, whenever i talk about canon i think about its inverse, apocrypha. if you go back to the history of biblical apocrypha, it kind of lays bare the motivations behind maintaining a "canon". protestants didn't believe the apocrypha were divinely inspired, and that was their motivation for making it apocryphal, and not canonical, to begin with. of course, that opens a whole well of biblical inspiration and the tension between the belief in the bible as a text solely authored by god and the reality of its creation as a multi-authored, patchwork, often deeply political text

this gets into a whole mess of biblical authorship and brushes up against a lot of stuff i simply don't want to dissect right after waking up, but i'm sure we can all get where i'm going with this: the reason the apocrypha were taken out of "canon" is that it's not "divinely inspired" and this intent echoes out into the whole discussion. the epilogues, beyond canon, pesterquest, they're just not divinely inspired. they're not smiled upon by god. (and quite often the "god" invoked here is an imagined version of andrew hussie that no longer exists)

i think at the end of the day "what's canon" is a deeply politicized argument that, whether we like it or not, rarely relies on the quality or even relevance of a text, and instead comes down to "i don't like the person that wrote it", and this is about 80% of why i've struggled to keep my attention on capeshit, despite my heart being open to it in theory.

as a writer, what's "canon" is what's useful to me. homestuck - especially the back half of homestuck - is a story that requires a lot of legwork to put together into a sensible thing, and people just don't do that leg work. and because of this, i try to give every part of homestuck its due process, because that's all text that was written with intent, right? skaianet wasn't canon to my work until i realized it was useful, and now it is.

as a reader, i do think rose laid it out best - there is a lot of homestuck to work with. so sorting it by its relevance, essentiality, and truthfulness does just work. the snapchats that weren't part of the credits were largely irrelevant and inessential, so their truthfulness didn't matter, right up until they did and jane fired cake lasers at everyone.

so with that in mind, here's how i feel:
canon - a text or part of a text that is presented as diegetic within a text (eg, Homestuck is canon to Homestuck: Beyond Canon and Burning Down the House, but the Snapchats are only canon to Homestuck: Beyond Canon, they didn't happen in BDTH)
noncanon - a text or part of a text that is not relevant to interpretation (eg, Secret of Mana is not canon to Umberto Eco's Name of the Rose, but it is to Homestuck)
dubiously canon - an interpretation relies on inference and implication but can't be written off as "noncanonical" because if we throw out inference and implication as a meaningful way to understand a story we may as well all kill ourselves now (eg, Undertale is Dubiously Canon to Deltarune, Homestuck: Beyond Canon is dubiously canon to Burning Down the House)
post-canon - an approach to storytelling that rejects a single canonical truth, opening up contradictory ideas, to convey its story (think post-rock, post-structuralism)

the issue, then, is when people pretend "post-canon" is "noncanon". the ideas presented are contradicting existing canon, but like. maintaining a proper, non-contradictory canon is an elusive and ethereal goal that will be fucked up just because like, human thought tends towards contradiction. despite what my beloved son detective conan says, one truth does not always prevail. and acknowledging the complexities and contradictions in a story as a natural, intentional part of them, and not a failure to create "the perfect story" is important.