The markdown editor breaks URLs that have a
 in them in the post preview. For example:
the URL is:
it works fine in the final result, though, so it's very minor.
I've noticed that the URL generator (highlight your URL, then hit the world-with-arrow icon) gets confused if the URL being highlighted has a close-square-bracket -- it thinks "aha someone already put the end of URL marker in for me, so I won't bother putting in another one", which prematurely ends the URL markup:
Rather than what should be: