I understand that you want the options to be easily available, but should we really start piling various preference options direction onto every page?
During Hovercards discussions, several people suggested it might be a good idea to upgrade the preferences system. The preference system could potentially be higher profile, and it could be re-worked to be more friendly to readers. Perhaps the initial preference page would focus on items intended for readers.
How about keeping "Enable Previews" within preferences, with the preferences system itself considered for future examination?