Kale is a Green-Green food. Green-Green foods are safe to eat as a regular part of a diet.
Guideline related quotes related to Non-Starchy and Green-Green throughout Geoff Bond's publications.
Eat at least 2 3/4 lbs of mixed salad and vegetables per day, consisting of "Green-Green” and “Green” foods. Of these, at least 3/4 lb should be mixed salad. Also include at least 5 cups of “Green-Green” leafy vegetables or 2 1/2 cups of other vegetables per week. ~Paleo in a Nutshell p.102
Specific references to Kale throughout Geoff Bond's publications.
Low-starch vegetables should be served five times daily. These are the usual items we call vegetables, such as green beans, broccoli, and kale— with the exception of potato, of course. We should also go easy on sweet potato, carrots, and peas, which are starchy-sugary and moderately glycemic. ~Paleo in a Nutshell p.48