This is a particular quirk of the situation that came up, but I don't think we're going to make any changes from it, given how rare it is. It requires the prefix to be on the end of a line to the point that the space we append after it can't fit on the same line (which is a couple pixel-wide margin) and the title that follows being a single word that can't fit on a line. Both scenarios will generally be rare, let alone in combination. That ends up causing the space after the prefix to be put on its own line, giving the appearance of a blank line.
