Sorry if this bug is a duplicate (could not find one). I'm posting something that was raised 2.5 years ago and rhythmbox still has not sorted it out. Found it while looking at various logs.
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* Now talking on #rhythmbox
* Topic for #rhythmbox is: Rhythmbox 0.9.2 is out
* Topic for #rhythmbox set by hadess at Thu Dec  1 07:14:23 2005

nekohayo: hey there, if anybody knows, I'm wondering if rhythmbox currently plays songs depending on their rating? (a 1 star song being almost never played for example) ? I am not sure of the current development status and could not find that info on the website

moch: if you select both repeat and shuffle, you get a random play order weighted on rating and time since last play. This is not well known. If you want it to be weighted just on rating, you can set the gconf key /apps/rhythmbox/state/play_order to random-by-rating. At some point we are going to make the play order selection UI a bit less broken.. I think it was just a hack to expose the random play order to begin with, but it's been like that for a long time now
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Isn't the solution simply to have a checkbox in the preference that says "[x] Prioritize playback depending on notations"? 

Then there would be a clear ui preference to set this, and no more need for the "shuffle+loop must be activated" hack.