Mixed language paragraph justification problem

I note under WP 1.5 that paragraphs with mixed languages (fixed width Chinese characters and English) can not be properly justified on both sides. Even when I used full paragraph justification, the right side always stay jagged and there’ll be some huge spacings b/n some English words dotted around the paragraph.

I’ve tried three different themes including the default, they all exhibit the same problem. In comparison, paragraphs with all English text behaves normally with proper justification on both sides.

Is this a known problem with WP.