Update:
I cleared the history on Firefox, no more gray horizontal ruler and “Edit” in the footer.
This is not the first instance where I’ve found I have to make special efforts on other websites because of potential issues that seem particular to Firefox, FYI.
Dear Clayton James,
Thank you for looking at my site. I’m not using additional plugins, I’m not aware of a theme feature that only shows up if I’m logged in while in admin.
I was not logged in to my website when viewing my website on Firefox or Safari.
Many thanks, Nigel M. Rodgers, for your kind assistance.