Upgrading
#MacOS Sequoia to 15.6 has, weirdly, affected some of my font settings. In Mail it changed my fixed-width font setting to "Helvetica 13", so I changed it back to "SF Mono Regular 13". It also appeared to turn Apple
#font smoothing back on, which I don't like because on my 1440p external monitor it makes the text look a little bolder, less sharp, and somewhat distorts the shapes of the letters. So I turned it back off with this "defaults" command.