5
For changes to theme.html to show up, you'll need to enable the "update module templates from themes/yourtheme/templates folder" in general preferences.
It is not the most clear description, but it'll check the theme's theme.html for changes and recompile it (replace the one in templates_c folder, which is why clearing this folder works, too)
When the theme is as you want it to, turn off the "update module templates..." option for better performance.
"When you can flatten entire cities at a whim, a tendency towards quiet reflection and seeing-things-from-the-other-fellow's-point-of-view is seldom necessary."
Cusix Software