There is no real fundamental reason why a dark compound coating should not have a strong chocolate flavor.
Coating is usually used for a technical reason (the higher melt point) or because of price considerations (it's cheaper) or both.
From one of your other questions I am going to infer that the higher melt point of compound is a main reason you're using it.
If you're using a dark coating then the simple answer is to buy a better coating. There are some that are very difficult to tell apart from bulk chocolates.
If you're using white or colored compound the answer is to add very small amounts of a very good chocolate essential oil flavoring. If you do that it's very important to make sure the coating is at a high enough temperature (100F at least) and do a very good job of incorporating the flavoring oil. If you don't it can leave streaks and deliver uneven flavor.
You can also use the chocolate flavoring oil in the dark compound if you are having trouble locating a better tasting dark compound.
However, Lynn and Antonino are essentially correct: the chocolate flavor will probably not be as "good" as if you used real chocolate because the oil is likely to be one-noted. However, the chocolate flavor will be more intense.
Not all of us live in places or cater to markets that can afford to use expensive or real chocolate. While there is no way to turn a shrimp into lobster, we can work as hard as we can to make the shrimp the best it can possibly be.
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@DiscoverChoc