P.S. Don't reply to a Digest to answer one of the emails and keep the whole Digest in your reply.
Blame Gmail: their reply box ruined (old school) email etiquette for everyone.
Gmail (or Outlook, or any other mail client that defaults to top-posting) didn't break email etiquette. People broke it when they became lazy and stopped trimming their replies.
That being said, I switched from digests to single emails to get around the issue. Sure, I get more messages this way, but at least they're legible.