When facts about an author's intent/the production of an artwork can't be guessed from the artwork itself, can these facts matter to the interpretation of the work? Or does it only matter what an informed audience of the authors contemporaries would have been able to infer from the work?
This seems to be a major debate in the contemporary lit, but...
There doesn't seem to be a sharp/principled line between what the author knows vs. what "their community" would know. Rather we have a gradually increasing body of facts available to...
- all people speaking the same language as the author
- all people speaking the same language, living at the same time
- all people speaking the same language, living at the same time in the same country
- all people living in the same town
- the author's friends
- the author themselves, just after they wrote the work
- the author at some moment, while at work on the book
Actual art scholars' practice seems to be (so far as I know!) to ignore biographical facts when they speak against an otherwise motivated interpretation (e.g. the poet says they didn't intend any symbolism of this kind, or that The Wizard of Oz is just an elaborate political allegory), but to take them into account when they allow for a much stronger/more interesting interpretation (e.g. the artist reveals that she copied the lines in an abstract painting from pornography).
Suggestion: Everything about an artwork can matter to the "interpretation" of it e.g. theories of what happens in the story, what's ambiguous, what themes there are etc. But interpretation isnt the job of guessing what the artist, or their community or anything else is about. Rather, the point of interpretation is to facilitate valuable engagement with works of art (=the Kantian free play of the intellect and imagination etc.) by coming up with the most compelling possible interpretations. This is USUALLY served by telling us facts about the artists' community, and sometimes served by telling us facts about the artist, since interesting features are likely to arise by way of the artist consciously or unconsciously putting them in. But, given this aim, no facts - even facts about eery resonances with events after the production of the art- are out of bounds to the literary/art critic.
So I think facts about the author's intentions can matter, but only for the same reason that facts totally unknown to the author can matter. e.g. Here's Nabokov bringing his extra knowledge of entomology to bear on Kafka's Metamorphoses:
". . . neither Gregor nor his maker realized that when the room was being made by the maid, and the window was open, he could have flown out and escaped and joined the other happy dung beetles rolling the dung balls on rural paths" (Strong Opinions 90-91).