If you take a look at the permission on the manage permissions panel, you will see a column after the information icon… some permissions have an icon or two in there too…  you can hover over the icon for the meaning, but one is that it also has to be activated and the other is that the permission is ignored for guests…

so post rating is not permitted by guests…  mainly because they could stuff the vote and we cannot really record if they voted or not…

I would think that should be an option for the forum administrator to decide.

Lets face it, In this FAKE social media world everything (friends, likes, fans, yt likes, etc) can all be had for a price.

we actually have thoughts next time we update the plugin of trying to add it in…  its not as simple as a permission though… have to write several portions of it…   when it was written, didnt anticipate folks wanting guests to vote (or anyone to vote as many times as they want)…