You can check for problems caused by a corrupted localstore.rdf file.

• http://kb.mozillazine.org/Corrupt_localstore.rdf

If you do not keep changes after a restart or otherwise have problems with preferences, see:

• http://kb.mozillazine.org/Preferences_not_saved

If you have software like Advanced SystemCare that might reset some files to older versions to protect these files against changes then check the settings or uninstall this software.

Thank you!

The solution above didn't work for me. So I tried this instead.

Go to about:config and find the flag browser.uiCustomization.state. In its value (a string) remove any entry that has "readability" in it (there should be three of them for the three buttons).

Click OK and restart FF and the buttons will stay removed.

Good luck.

Hi The Readability toolbar icons keep reappearing for me. Using Firefox for mac ver 30.0.

I amend the following in the browser.uiCustomization.state field FROM: {"placements":{"PanelUI-contents":["edit-controls","zoom-controls","new-window-button","privatebrowsing-button","save-page-button","print-button","history-panelmenu","fullscreen-button","find-button","preferences-button","add-ons-button","developer-button"],"addon-bar":["addonbar-closebutton","status-bar"],"PersonalToolbar":["personal-bookmarks"],"nav-bar":["readability-toolbar-read","readability-toolbar-save","readability-toolbar-kindle","urlbar-container","search-container","webrtc-status-button","bookmarks-menu-button","downloads-button","home-button","social-share-button","abp-toolbarbutton","lpt_lastpass-compact-btn","RIL_toolbar_button"],"TabsToolbar":["tabbrowser-tabs","new-tab-button","alltabs-button","tabs-closebutton"]},"seen":["abp-toolbarbutton"],"dirtyAreaCache":["PersonalToolbar","nav-bar","TabsToolbar","PanelUI-contents","addon-bar"],"newElementCount":0}

TO: {"placements":{"PanelUI-contents":["edit-controls","zoom-controls","new-window-button","privatebrowsing-button","save-page-button","print-button","history-panelmenu","fullscreen-button","find-button","preferences-button","add-ons-button","developer-button"],"addon-bar":["addonbar-closebutton","status-bar"],"PersonalToolbar":["personal-bookmarks"],"nav-bar":["urlbar-container","search-container","webrtc-status-button","bookmarks-menu-button","downloads-button","home-button","social-share-button","abp-toolbarbutton","lpt_lastpass-compact-btn","RIL_toolbar_button"],"TabsToolbar":["tabbrowser-tabs","new-tab-button","alltabs-button","tabs-closebutton"]},"seen":["abp-toolbarbutton"],"dirtyAreaCache":["PersonalToolbar","nav-bar","TabsToolbar","PanelUI-contents","addon-bar"],"newElementCount":0}

Click OK and restart Firefox but the 3 Readability icons keep reappearing on my the left hand side of my toolbar. Am I doing something wrong or is there another way to prevent this from happening?

Thanks

Found alternative solution that worked. https://support.mozilla.org/en-US/questions/995019#answer-599880

Gingerbread Man's solution:

    Type about:config into the address bar and press Enter.
   Press the big button to bypass the warning.
   In the search box, paste extensions.readability.first_run_complete
   In the search results, double-click extensions.readability.first_run_complete to set its value to true
   Restart Firefox.
   Right-click an empty area of the tab bar and choose Customize. Place Readability's icons wherever you like. 

The problem you're describing is a bug in the add-on. I can confirm it, as do others who've posted reviews. Contact the authors of the add-on using either the "Support site" or "Support e-mail" links on the add-on's description page.