I use FormatMatch to strip out text formatting. It’s no longer available in the App Store so I guess the developer has abandoned it (although it’s still available for download around the web — just Google). Unfortunately, FormatMatch is not compatible with Yosemite/El Cap’s “Dark” UI mode, where the menu bar turns black/charcoal. The icon’s black so this causes it to disappear.
Here’s updated icons for FormatMatch if you use Dark mode. To install them, right-click the FormatMatch app in the Applications list of Finder, and select Show Package Contents. Navigate to the Resources folder, and drop the two files in there (StripItOn.png and StripItOff.png) overwriting the existing icons. Then quit and restart FormatMatch.
This isn’t a technically correct fix because a good app should have icons for both standard and Dark modes. Additionally, I suspect somebody cleverer than me can also add in Retina icons, which are also missing. But until that happens these icons will suffice.