And is it recommended or not recommended for a newbie to attach a long safety leash to the back of his or her harness ?

As Gateman stated the long leash that attaches at the back of the harness is really for unhooked and bar pass tricks.

I feel though if you use a short leash attached to the front of your harness and have the safety on the loop in "Expert" mode you can put a lot of load on you back if the you accidentally unhook or if the front lines have a lot of twists in them and the safety line doesn't slide properly. The reason the bar pass leash attaches to the back of the harness is so if you are being dragged by the kite your body can fold like a taco.

Hopefully once someone is doing more complex tricks they fully understand the safety system and it's failings. Then they need to decide which is the best system for them and what they are doing and are not driven by fashion or how others setup their safety.

The biggest problem with the rear attachment is that it is difficult to activate the secondary release which will get rid of the kite altogether when you are being pulled backwards through the water by a looping kite.

If you are not doing unhooked handle pass tricks I would recommend a front release. Maintain minimal twists in the front lines so that the bar travels freely too if a release is necessary.

That's a great vid, thanks