This is sort of an extension of ticket #1664.
There is an item in the Preference settings for "Composer":
Rich Text (HTML): Markup syntax: None/Markdown
From what I can see, this item is somewhat mislabelled. When
"none" is selected, new messages have "Plain text" pre-selected.
When "Markdown" is selected, new messages have "Markdown"
pre-selected. I can change that setting at any time, though.
If my observation is correct, a better label for this item might
be:
Default markup (rich text) syntax: None/Markdown
Which means that we are selecting the mode that will be preset
when a new composer window opens.
