Harald I wonder why you are using dither-style feathering though, as a standard threshold might look better with typical the image outlines, which are just a gradient alpha. The purpose of dither patterns is usually where a homogenous area needs to become transparent, there you can't solve it with a single tweaked threshold. If you know what you're doing it's fine of couse, you might have your reasons.
Because my texture is made by the ink flow diffusion drawing method, there will be many places with high transparency. If I don't use dither, the top model will have many very transparent areas that block the objects behind. Visually, it looks like it is blocked by air. For example, the trunk of the tree in my screenshot. If I don't use dither, part of the outer side of the trunk will also block the objects behind.