For proof, read any comments section here, particularly one with an exasperated Blaastar, and you will see readers make up any story they want.
Hey, I like reading Blastaar's comments. I think they're one of the most enriching commenters on the site, occasional sharp tongue notwithstanding.
I guess my point is that whatever the author is thinking is always irrelevant because we only have the text.
Largely yes, but it's sometimes prudent to have at least some awareness of who's written the text and what views and experiences may have informed its inception – even though that can never really refute what is clearly shown/told in a work, mind you. Context beyond the presumed intention – like time, culture, personal experiences both of the person interpreting as well as the author – is still relevant to an interpretation, whether we like it or not (which does not mean that it validates or invalidates an interpretation. It's just reasonably helpful additional information towards understanding how different people might arrive at different conclusions from the same text).