@edsuom Is that "boosting with a comment" / e-mail's "forwarding inline with a comment at the top"?
There are some things I wish I could do on Mastodon (or perhaps the limitation is in the web ui?) but I keep fearing that, if I tried to write down a list of these features, I'd end up with MIME... reminds me of Greenspun's tenth rule, although I guess jwz's law might be a bigger concern :-P
(Jokes aside, MIME allows me to interleave images with plain text, for example. Can that be done here?)