Weird Waveform and Histogram spazzout I was just wondering why these weird lines/gaps/spikes happen to waveform and histogram as soon as a modifier is used? Can something be done against this? 
And why is the Histogram in the preview so incredibly tiny and pixelated?
The gaps are quantization gaps. If your image is deeper bit depth, you will have fewer gaps. Compare against a Cycles render at 32 bits float stored as an EXR versus say, an 8 bit TIFF.

Some 8 bit manipulations will squeeze values together or pull them apart, making the combing more obvious.