So glad you've picked this up!
And I know I did that but I was silly at the time so would it be possible to undo that change and hardcode the blank spaces outside <span> instead? This would make it consistent w/ bug 4640 (see https://github.com/dreamwidth/dw-free/pull/184/files). Reasoning for that is that users can't see blanks spaces at the end of props in Customize, and this makes styling labels harder.