Rated 3 out of 5 stars
In order to make it work you need to run version 2.0.rev281.1. Then it will work in both the context menu and the status bar- which lives in PaleMoon and has been obliterated in Failfox.
The latest version was as if it wasn't there. Run PM and roll this back one version and it will work just fine.
EDIT: It actually is working- too well. It displays in both the context menu and the status bar- and then it remained there until I removed the extension. There was no way to toggle it and even Organize Status Bar could not remove the display.
The add-on is working. It just does not have the information in the status bar, to have the statistics please right click and choose Word Count Tool.