In english though, if i ask "who reads" the answer would be fine as "they do" (plural) or "he/she does" (singular). How would you ask the question to be specific? I'd say the english question doesn't specify whether its plural or not, and so asking for a specific plural/singular answer in Italian isn't that fair.
"they" has specific number, always plural. You cannot say "Who reads" in the "they" form. "He, she, it, everyone, or who reads", but "they read". So, if you know that who is plural for sure, you might ask "Which group reads?" "Do they read?" Do you read?" So "Chi leggono?" would still be "Who reads?" or "Who are they that read?"