Thanks Symmetric!
And I have to retract my statement:
Quote “After some research I found, that Blender sets the max. of 4 bones per vert by default, because it seems to be the value for many games.”
I did some more tests with other meshes and the Automatic Weight funktion might assign more than 4 bones:
I konw, there are bones assigned, which are not needed, but still: Blender does this!
Fortunately has this weight tool called “Limit Total”, so it’s possible to cut things down to 4 bones per vert.