Is the hinge design much more stable than the other v-hinge, vice grip designs? Less flexing?
does the tension cable actually help?

What's the reason for the 1kg extra weight compared to other dahon models? The specs mention steel fork?

Another thread mentioned QR skewer with disc brake is bad. What about skewer bolts with aluminum nuts to 6Nm?

Extra dropout width problem with suitcases?

https://usa.dahon.com/products/launch-d8

Just saw this thread, it was from before I was active in the folding group. I can answer some questions.

I haven't ridden the Launch yet; On paper the original Jaws hinge should be more torsional stiff, as the lever provides adjustable takeup, and doesn't rely on a hinge pin when folded. The NEW Jaws hinge should be better, as the jaws are tapered; I don't know if the old serrated jaws stay flat or loosen up.

The Deltec cable should help. I got tired of waiting for their "Add-On" version and made one myself from Kevlar line, for a Speed D7. It's tightened the hinge right up. Used to need to adjust hinge latch monthly, now none needed in over two years. Changes bending stress on hinge to compressive shear, works much better with that small a pin span. Dahon has run hot and cold on Deltec, adding to models, then removing. I guessed that perhaps the welded attachment point in front of frame was pulling loose in fatigue, I would have made it longer; On their Japan website they show a new design where Deltech attaches in front to ring around fork steer tube; Not sure if that confirms my theory. Steel frames on cheaper Dahon D6 still has Deltech; Steel doesn't fatigue as easily as aluminum. That's my theory. My implementation wraps the Kevlar around the head tube and bottom bracket shell, does not rely on welded tabs, bulletproof.

QR skewers are supposed to be bad with disc brakes, I think the main motivator for thru-axles now. However if caliper and/or dropout slot are oriented properly (slot facing forward, caliper high), that will impede axle pullout under braking. Also, 20" wheels have less moment arm for same braking thrust versus larger wheels, that helps. This is mostly an issue for the front, although if rear axle is loaded heavy enough under braking, it can also generate the torque needed.

EDIT: The additional weight I suspect is due to the disc brakes and calipers, compared to non-disc bikes. This feature I welcome as it will make the rims more durable, especially since small wheels make the sidewalls wear faster; EXCEPT, Dahon in their infinite wisdom made two mistakes with those brakes; 1) Their "safety brake", offsetting the discs inboard 15mm, which means different hubs and calipers than standard, and 2) cheap single-side mechanical calipers (push only on the outboard side of disc and rely on disc flex to hit the inboard pad) that you would want to replace, but due to the offset, you can't without also changing the hubs on both wheels. I can see the advantage of offsetting the discs inboard, but only if they provided good calipers with them.