I tried the "reply by email" feature of Phabricator; it works pretty well, the only problem is that lines are broken up to be less than 80 (I guess? did not count) characters. This looks ugly and also breaks some formatting.
The email sent by Phabricator (and thus my response) does not have those linebreaks, so this must happen either somewhere in the WMF mailing architecture or in the Phabricator email-to-comment conversion.