Understandable, is the built-in Reader view. When you open an external link from reddit the reader downloads that page's full HTML to run the Readability parser on it (reader.js → fetch(url)). Since Reddit links can point to any website, that fetch can target any domain — and a browser extension can only fetch cross-origin from sites listed in its permissions. There's no fixed domain list that covers "wherever a Reddit link happens to go," so it resolves to .