pointless Rated 2 out of 5 stars

a) open a file named "userChrome.css" in the "chrome" directory of your profile folder with your favourite text editor.

b) append the following two lines to the file (might not display properly):
#bookmarksBarContent .bookmark-item > .toolbarbutton-icon { visibility: collapse; }
#bookmarksBarContent .bookmark-item > .toolbarbutton-menu-dropmarker { display: inherit !important; }

c) save the file and restart firefox

result: same as 'hide favicons'
plus: works on all systems

This review is for a previous version of the add-on (1.3.3).