There exists a wealth of knowledge within the eZ publish kernel source code itself. Much of this code is documented inline, take a long look at the generated source code documentation built from the subversion trunk very regularly.
It's not that I know of. The best places to look is the doxygen documentation (generated from the source) http://pubsvn.ez.no/doxygen/index.html and the source code.
I stumbled across this one. Noticed the setting when investigating the set/layout module and followed it through the source from there. There is quite a bit in eZ like this.
Be aware it causes issues with mailto: links http://issues.ez.no/IssueView.php?Id=7904