[e.k.]

... not my most important topic, but anyway, I think it's a useful proposal ...
If you find the time to implement this request I'd also vote for "hide all empty stars", the line up issue is only relevant if the rating stars are the very first entry in a format line.
Btw: %RATING_STARS% seems to be missing in the drop down lists of the Song Title Formatting dialogs. I used it before but can't remember where or how I discovered it.
It could be an alternative to the proposed option  "show unrated stars yes/no" to offer additional format strings like %RATING_STARS_NOT_EMPTY% (a better / shorter name would be highly welcome)

It´s in the Fields list "Rating" (Bewertung)