When adding text to a label in Clean theme the text appears as bold. If you try with a different theme (see screenshots) the same text in the same label is "normal".
Steps to reproduce:
1. Using the Clean theme, turn on editing, add a label and type in some text. Save and verify it looks bold (even though the HTML view confirms it is normal text)
2. Switch the theme to a couple of different ones and verify the same label no longer appears to have bold text.