Quite. This is a major reason that when I left elm for Gnus back in the 90s I never considered going back to anything like elm, or mutt, or gmail again. I need multiple mails open. I need my mails to appear in my editor so I can copy from one mail into a temp buffer if I need to, and I need them to stay open when I open another one. Gnus can do that without terribly much effort, because it's sitting atop an editor that can do multiple buffers natively. mutt can't.