I've updated the Weighted Words plugin, version 1.1 is now available for download here.
This release fixes a validation problem with the default search URLs, adds ! to the list of stripped-out punctuation, and adds an option to use "pretty" search URLs.
There are still character encoding problems. What I think is happening is that
strtolower() is ruining everything, and using
mb_strtolower() would be the most robust way to fix it. However, my server doesn't have multibyte string functions installed. If someone could help me test this, I would be much obliged.