I don’t know if it’s a temporary bug, but if it’s an “improvement”, then please revert back because this isn’t one for me, or give users a choice in the reader settings. Thanks!
EDIT: actually, if I may make a suggestion: if it’s not a bug, then consider simply altering the CSS to make pinyin on known words visible only on hovering. It’s a tiny little change, and it gets everyone the best of both worlds: new learners are encouraged to learn characters and not just pinyin (which I assume is the purpose of this alteration of the reader), but they can still get access to the pinyin to refresh their memories much more conveniently than by having to click on the word. And if you still don’t think it’s a better idea, at least make your new change an option in the reader’s settings, please!