The sprites and the trigger's translucent meshes are now all drawn in the correct order. The difference is subtle from what I had previously - palm trees were already sorted offline, which was hiding most of the issues - , now for 2D elements it looks always correct, even when turning the camera all around in editor mode. For the trigger's mesh it's an approximation and sometimes some trees close to the limits get drawn in front or behind depending on the camera's position, but I'm going to stick with it, at least for now.