What do you think of [spoiler]'d Furigana in [details]?
[details=巧み]
Details is dead.
[/details]
It seems that Furigana in [details] itself doesn’t work either.
<ruby lang = 'ja-JP'>巧<rp>(</rp><rt>たく</rt><rp>)</rp></ruby>み
Ruby is dead.
Though, of course it can be done with vanilla HTML.
I still can’t find a way to shorthand render Furigana without auto-inserting Furigana, or blur mode.