Related to the question on $\LaTeX$ math support, it would be nice to view the Markdown for questions and answers with nice “typesetting.” Yes, users with sufficiently high rep can click edit and then back, but that isn't quite the same.
Not a great solution, but I do one of two things:
Get your web browser to show you the HTML source code of the entire page, from which you can copy any post.
If your computer isn't fast enough, it takes a short while for jsmath to do its job. In that while, you can quickly select the text and copy it to clipboard. This works fine for me. I just reload the page, and quickly press Ctrl+A, Ctrl+C on Windows (which selects all the text in the page and then copies it to clipboard).