Browser extensions already have access to privileged APIs that websites cannot use, however, so providing this ability to extensions !== providing it to medium.com.
The kind of company that would abuse an extension API like this for marketing is just the kind of company I wouldn't trust for extensions, so even spammy marketing messages would still be a useful signal (to uninstall).
The kind of company that would abuse an extension API like this for marketing is just the kind of company I wouldn't trust for extensions, so even spammy marketing messages would still be a useful signal (to uninstall).