Is there an advantage to passing a Justification object as a reference (see juce::GlyphArrangement) ? From what I understand, your coding standard suggests that the object is small enough that it should be pass-by-value.
So, the best-practice advice from the guys who actually write the optimisers is: Always stick to pass-by-value if possible, and only use references if the price of calling the copy constructor is very high.
The class is wrapping an integer - "the price" can't be that high?