Give way to the right

We finally solved the mystery of the strange driver behaviour in our village. This came up at our aperos evening.  
The main D road goes right through the village but we have observed that many drivers on it give way to the Trebes road which joins it. We have taken the precaution of doing the same but not knowing why we do so here and not in other similar situations elsewhere. This is the answer

This sign at the entrance to the village means that you have just lost your automatic right to priority and must give way to the right. 


This is the sign when you're leaving the village and back to having priority.

In practice in Villaier, people mostly only observe it in relation to the (fairly main) Trebes road but I have been given way to when coming out of a very minor side street.
It wouldn't be too bad if the application of the rule were consistent but you definitely can't rely on it! 
I wonder who spread the rumour that the French had abandoned "priorité à droite"