Short answer: no.
I have been using the Fedora mailing lists since Fedora Core 2. I have
spent time setting up mail programs to sort all incoming email lists
into nice, neat categories that are easy to read through. They don't
need a damn browser that has become a bloated catchall do-all tool for
everything under the sun.
Nothing is stored locally with Discourse so,
you have to be online to do everything. I can't read anything on
Discourse offline at my leisure. The confused, incongruous threads are
difficult to read without having to scroll up and down constantly. With
a mailing list, everything that is pertinent is right there before you
to peruse easily and quickly.