an easy example how to remove all off curve points see https://github.com/typemytype/RoboFontExamples/blob/master/pens/removeOffcurvesPen.py

No, trying to close a path for instance. Or to make 2 redudant node one. Currently the snap-to seem to apply to the target node as well.

command + c --> cutting segments out alt + del --> breaking contours on the selected points

This case is unfortunately a consequence from FLS. Superposed nodes: when deleting one of them, the remaining one should inherit the handle length. Instead, a new curve is calculated and differs greatly.