Chamfer

http://joxi.ru/Z4B2UxjKTJCfRg_-Ps0Â

I don't think the top example is necessarily incorrect on Nvil's part... NVil is creating geometry that should hold up better after subdivision (quads and triangles). With a little manual editing, it can be made fully subD. Blender is simply using an nGon.  Of course, both methods could have their place, and I think this might be a good example of where an option to tap the Capslock key to toggle between the two behaviours would be useful.

 I think what D. is pointing out is that the new vertices can create overlapping polygons afterwards which are very difficult to clean up.

Solution is stop the chamfer once the new vertice collides with the border  (and then welds the 2x vertices)

http://joxi.ru/OXB6UxjKTJAjTiTwgzAÂ

https://www.youtube.com/watch?v=IOB2wi_tAvo