I’ll make the simple argument-- I don’t want to write summaries for posts and I don’t think the first X characters of a post with a title translates to the correct preview content. Showing a random 300-500 characters that start my post that is suddenly cutoff doesn’t seem great to me. I spend (minimal) time writing a title to let people know what it’s about. I don’t want to have a second step spending time writing another paragraph about what my two paragraph post is about. I don’t want to have to reread my post and figure out if the opening is the opening that many people may only see.