Oh yeah this was done all the time 'back in the day'. I don't know it it was safe or not though. It's not done so much anymore.
I use paramont crystals now or oil or shortening or butter to loosen the chocolate so it doesn't have such a sharp crack when you bite into it.
That is a really old school recipe 
Before the "melts" we have now, there was only the chocolate chips and the wax was used to help thin the chocolate so it's easier to work with. It's perfectly safe to do but you can also melt the chocolate and if it's a little thick, just put a little shortening (Crisco) in it to thin it.
Good Luck.
They still sell parafin wax for making candy in specialty shops, I use it when I don't have crisco.....
I use crisco most of the time, it gives the chocolate a nice shine as it thins it.
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