there is a tool for grammar/advanced spell check called Language Tool (https://languagetool.org/#more). It runs as a standalone app and as a server.
Some 3rd parties created a plugin that should enable integration of Xbench with this Language Tool. It is available here: http://www.projekt-partner.pl/?post=integracja-xbench-z-languagetool (page in Polish, but google-translable to English).
What you supposedly need to do is to download the plugin file from here: http://www.projekt-partner.pl/data/uploads/files/XbenchQALanguageTool.zip. It is a ZIP file containing a DLL and a very basic INI file. Then you are supposed to copy these files to the Xbench folder and after restarting Xbench a new option should appear in the XBench’s QA tab -> Check Group pane.
This, however, doesn’t happen for me.
Is it something that is supportable by you?