The molecular absorption lines dominate in very cool stars, and do cover the spectrum. Even cool regions of the Sun apparently do that, in CO lines. For much hotter stars, you don't have molecules or H minus, but you have bound-free edges of various species. The degree of scattering gets quite large-- from free electron opacity-- but we need to understand the thermalizing opacity to understand where the blackbody spectrum comes from. Free electrons in the vicinity of protons have some photon-thermalizing abilities, called "brehmstrahlung" (braking radiation) or "free-free emission" (it's the same thing), but I don't know if that ever exceeds the bound-free edges (generally I think not).