I've got a manual so I can't say for sure on the CVT but I suspect the coasting senarios are similar. I usually coast in neutral (sometimes ICE off) depending on the condition of the battery charge. If the pack is mostly full the car goes in N for the downhills, if the pack needs some help I'll leave the car in gear. Sometimes I'll split the difference, gaining speed in neutral till I'm a bit over the limit and then I'll put it in gear to help brake the car and charge the battery.

I should think that you would want to match the speed of the engine with the speed of the car when putting it back in gear. I can't really say if you are hurting anything. One of the reasons I got a manual is so I wouldn't have a need to answer that question.

Some say that it is better to leave the car in gear because the engine goes to fuel cut mode, while the engine must use gas to idle in neutral. This has not been my experience. You get better mileage in neutral and you don't get slowed down by engine braking. You get infinate mpgs coasting with the ICE off but that can be dangerous.