It turns out that both of your questions regard expected behaviors.
The format is only applied on a visual level so as not to change any value coming in (we don’t want to change values you supply - only how they’re visually represented).
As for removing the arrows, Yousuf recommends using this: https://www.w3schools.com/howto/howto_css_hide_arrow_number.asp
Before the theming update we had removed them from Chrome but not Firefox. It sounds like going forward we’re going to be more hands-off since we’re allowing and encouraging customers to develop their own CSS. AS a result, we’ve removed the Chrome-specific removal of the arrows.