The various markup engines that Jekyll uses may have some issues. This page will document them to help others who may run into the same problems.
If your link has characters that need to be escaped, you need to use this syntax:
Versions 4.1.1 and higher do not obey the notextile tag. This is a known bug and will hopefully be fixed for 4.2. You can still use 4.1.9, but the test suite requires that 4.1.0 be installed. If you use a version of RedCloth that does not have the notextile tag, you may notice that syntax highlighted blocks from Pygments are not formatted correctly, among other things. If you’re seeing this just install 4.1.0.