allow visual formatting options for questions/answers. Font, color, background, border ...
The visual appearance of information is a huge learning aid.
I would love to see Mnemosyne add support for such features. It could also provide some very interesting data about how visual cues can improve recollection.
An implementation should of course allow support for importing formatting from other software in the future.
I'd like to open this RFE again. What I meant was a WYSIWYG editor. Writing HTML in longhand is not really so great.
What makes formatting useful is the use of a variety of colors and appearances in the same answer/question. It makes visual recall of text much easier.
I expect you know more about that than me, but I know that for me it makes a big difference if I can visually recall the answers.
A start might be making the 'Configure > Card appearance' options card specific and available from the right click context menu
Did you already have a look at 'Configure Mnemosyne - Card appearance'?
Apart from that, you can also add any html you want to your cards.