With a fresh build from scratch, e.g. on Mac OS X, startup of jedit.jar produces warnings like this:
"initPLAF failed to set required l&f".
The reason for this is as follows: jEdit property "lookAndFeel" is unset (null), but the system defaults to UIManager.getSystemLookAndFeelClassName, as is correctly determined by jEdit.getPLAFClassName. The subsequent comparison seems to be mangled a bit, though.
The included patch tries to sort this out, using the string class name of jEdit.getPLAFClassName more uniformly.