Originally Posted by kovidgoyal
Going to Preferences->Advanced and clicking check database integrity should automatically remove unused tags
sorry Kovid - that didnt work for me.
I did it, and also restarted calibre after it,
but the same tons of unused tags (showing  usage in TAG view) remain.
Dont know if I mentioned it already, but I have to keep on using v.0.6.29 since I'm on an old fedora fc8 version.