we have recently updated the rule creator at http://www.languagetool.org/ruleeditor/. It helps you write your own LanguageTool rules, either for personal use or for the community. The example sentences that need to be specified for each rule are now checked against at least 50.0000 documents from Wikipedia. This is supposed to help against overly strict rules that complain about sentences which are actually correct.
Any feedback is welcome.