After 5.6 we have new feature which allows us to cut sprites mesh to avoid drawing transparent pixels, but in my case it does no effect on sprite mesh.
Here is official documentation about it:
I should get this kind of outlines for sprite meshes:
I cut my sprite like this in sprite edotor with edit outline tool:
Here is how sprite mesh looks now, it is optimisation because rasrteriser do not need to draw transparent pixels, also there is mach less problems with sorting.