Good thread idea.
The Norwegians mostly disregarded ornamentation, as you described. I think it was on a conscious level for practically all black metal musicians.
Death metal, on the other hand, had several bands who did not use it, and a lot who did (Atheist, Morbid Angel, etc.). I think it is important to note that some well-regarded bands such as Bolt Thrower, Sepultura, and Deicide did not use ornamentation, except maybe in solos. Then you have some bands like Paradise Lost who may have played slower, but still used it. I think Necrophobic used it too. Swedish death metal tended to be more "pleasant", so it would make sense to steer clear from a lot of the straight-forwardness found in heavily-influenced-by-Slayer death metal.
So for death metal it depended upon what was being accomplished. Black metal musicians did not want to express themselves that way. In fact, I think they may have seen ornamentation in Swedish death metal--swe dm being something they wished to get away from--and so chose to forgo its use.