It falls in two categories.
1. Routing requirement. The line is restricted on where it can run and it has to turn a corner to get to the destination. 90 degree bends with the outer corner cut off can totally eliminate reflections. The 135 degree bend comes from digital design where the layout programs do not cut the corners of bends off. This 135 bend has a low enough reflection for digital signals that it is acceptable. The 45 internal angle bend is totally unacceptable and should be avoided.
2. Electrical requirements. The step in impedance is intentional for filtering purposes or impedance transforming purposes. The step can be modeled as a shunt reactance. Your simulator program will take this into account. T junctions also fall into the intentional discontinuity area. Adding extra triangles of metal will only make things worse because it add extra unknowns to your design.