I tried using jspwiki.urlConstructor = ShortURLConstructor and it took me a quite amount of time to see that this causes a problem:
The editor toolbar is not working anymore, the quick preview under the editing text area eighter.
The web console of firefox shows that there is a syntax error in line 13 in jspwiki-edit.js.
The line highlighted is:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
Using the ShortViewURLConstructor or the default "fixes" the problem.