Thinking about what the Venn diagram of readers who don't comment on fics and people who live by the rule "If you don't have anything good to say, don't say anything at all" would look like
I do believe that when a reader choses to comment or not to comment on a fic it usually has more to do with the person than it has with the fic.
There're some people who won't say a word even if they're completely in awe of the work. There're people who praise every work they've liked half a paragraph in.
Sometimes readers open a fic because of the intriguing tags, and don't say anything because they aren't really that into pairing.
Sometimes people are too worried about how they might sound stupid, or think that this super cool author won't care about a mere mortal's opinion.
Sometimes people forget, because they're too busy, or have ADHD.
Sometimes people expect you to comment on their fics in return, you don't do it, so next time they don't say a word.
Sometimes people don't like some part, big or small, but also don't want to discourage you from further writing.
Sometimes people find your work shitty, but not horrible enough to confront you directly. Maybe they'll complain about it on tumblr or twitter without naming names.
