I also enjoyed the Quora digests until one day the links stopped going directly to the threads but all pointed to a feed page. I assumed this was another dark pattern to boost pageviews and unsubscribed.
I prefer the feed page. There's usually more than one interesting link in a Digest and the pages aren't exactly lightweight on my phone. I wouldn't be so quick to call it a dark pattern; could be a reasonable UX decision based on how people use the emails.