While editing this question, I noticed that the ruby (or furigana) causes problems with vertical alignment when used in the title. It is okay that the ruby takes up some vertical space, but it should not affect vertical alignment. In the title of the question that I linked or of this question, the ruby is vertically lowering the entire character that is rubied. If possible, I think this should be fixed. In a strict view, this is a bug, but it may also be considered as a feature request. Sometimes, the vertical alignment appears correctly as in the title of this question
This is reproduced with Firefox but not on Internet Explorer or Chrome according to the comments below.