Discoverability based on more specific categories, like "humor/comedy" "movies" "advice" would be more helpful than trying to triangulate between what a writer/author reads and what a new reader is reading. Writers who are more open-minded subscribe to newsletters that have nothing to do with the content they write about. If a reader is interested in more "humor" writing, for example, it doesn't make any sense to suggest a travel newsletter simply because the author of the article they are looking at reads it, and you are deeming it higher quality because of that when it may not really be better than other newsletters in the same category but rather a reflection of a personal relationship the author has with another author. To a lesser extent the same goes for the readers of a publication. People have eclectic tastes and are not monolithic. But as a reader if I'm enjoying an article under the category "movies" then I would appreciate seeing articles that are tagged with related terms like "film" "cinema" "movie recommendations" "movie reviews." The lack of tagging or more nuance in the categories Substack offers really limits discoverability.