We urgently need an answer whether Atlassian will repair this functionality. Currently theming and (more importantly) the Look and Feel API does not work at all. Only very few lookAndFeel attributes are taking effect (sub-attributes of content to change the page background for example). You’ll able to find some of the other persisted CSS values within https://foo.atlassian.net/wiki/styles/colors.css but obviously deprecated selectors are used.
Can we expect that this will work someday (and when) or will Atlassian drop this api?