I'm the author of this post, happy to answer any questions. About me: I was formerly a director of product at FB and a founder of Firefox. My YC startup became FB's first acquisition. I'm focusing more on creative writing these days (wrote the Silicon Valley spec script and the Theranos parody that have come up on HN a few times.) Aphantasia was a pretty weird discovery for me given this new focus.
I often wonder whether the imagination can be improved like a muscle since I have trouble holding mental image outside brief flashes. I'm not sure if you can relate, but trying to picture something in my mind often feels as though I'm trying to recall the fleeting details of a dream; the harder I try the more foggy it becomes.