When I attempt to save a file with an upper case "J" in the name, Thunar changes the J to lower case. The same thing happens when I attempt to rename a file. Thunar acts as though it doesn't have an upper case J in its font.
Created attachment 7974 screenshot I cannot reproduce on thunar 1.6.15 nor 1.8.1. Please give us more details such as which distribution you are using, gtk version, whether you can reproduce the problem with other file managers and the output of: locale xfconf-query --channel xsettings --property /Gtk/FontName xfconf-query --channel xsettings --property /Net/ThemeName
Problem Solved The problem I was perceiving is in the design of the default Noto Sans 9 typeface: the lower portion of the capital "J" is the only letter in the Noto Sans 9 alphabet which extends below the others -- hence I was seeing it as lower case. I changed the default typeface to Arial 10 and eliminated the problem. Many thanks to everyone at Xfce!
Thanks for the update, closing.