Ever wonder if we interpret that scripture backwards? We usually hear it in the sense of, “If you’re wicked, you won’t be happy, so don’t be wicked!” But it could just as easily mean, “If you’re happy, then that’s a sign that you’re not wicked.” I think that, most of the time, that’s the more useful perspective.
Given the context of the scripture, I don’t think the standard interpretation is backwards.
I agree with you. Alma’s saying “If you are wicked, then you won’t be happy,” or, in mathematical notation, W→¬H (wicked implies not-happy).
My point is that, if we take Alma’s statement literally, it also says that a happy person is not wicked (because if he were wicked, he wouldn’t be happy). The value I see in that view is that it helps resolve guilt in people who have repented of their sins, but who still wonder if they’ve been forgiven.