In my (non-English speaking) country it's completely misused. At some point somebody made the association that it was a symbol for general swinging and that's how I've seen it most used. It doesn't have an interracial connotation. Give the meanings of 'spade' it makes little sense but the original sense was lost in translation.Does a majority of black people in Europe know the signification of the QoS ?
In any case, I don't think the sexual connotations are identified out of swinging circles.