Not necessarily. I've used Outlook Express and found it a pain in the neck
to paste pictures, even when it was set to use Rich formatting. The
pictures ended up as attached files and not properly placed within the
message. The same sometimes with formatted text; I usually need to go back
and fix (if not start over from scratch with) all the text formatting.
Far easier to just click Forward and then edit it down to what I want.
Perhaps Thunderbird works differently.
Andy