Does the job, unfortunately affects other functions too. Rated 3 out of 5 stars
If the dev. finds a way to have the add-on running and be able to delete bookmarks. I'll give this 5/5.This review is for a previous version of the add-on (1.7.1-signed.1-signed).
Try the non-plus version
The non-plus version does allow bookmarks to be deleted. It is at https://addons.mozilla.org/en-US/firefox/addon/disable-private-browsing/