There are some really fundamental issues of understanding that are missing here. Key among which is that torque splits are marketing jargon that have almost nothing to do with real life. You cannot say whether the S3 runs 85/15 , 90/10 or 95/5 front to rear because we dont have access to the programming and we haven't measured it. What we can say is that mechanically it lacks an epicyclic centre differential, so it is unable to run with a mechanically fixed torque bias like a BMW or an RS5. The default mechanical layout is therefore fixed at 50/50. What the software does with the coupling is variable, both between models and according to all manner of other dynamic factors, including yaw rate, steering angle, which gear you are in and what the ESP system is monitoring. This dynamic adjustment of torque transfer is highly variable, and differs from moment to moment, but it's range is variable from 100%front, 0% rear, to 50% front, 50%rear. This is its fixed design range. There are many other factors to consider though that in real life will expand that envelope.
This torque spilt everyone keeps banging on about is entirely dependant upon a key factor that is consistently missed. This torque transmitted along driveshafts only exists if there is something for the driveshaft torque to react against. That reaction comes from only one place (well, two if we also account for the pseudo front Limited Slip Diff, but that's another complication we ought to ignore for the moment). That key, fundamental part of the jigsaw, is the tyres and their grip on terra firma. It takes almost no torque to spin a transmission system with no load on it, which is why your dealer testing your Haldex coupling by showing you your car on a lift with all four wheels spinning merrily away is an utterly useless test - in the same way as you being able to bench press 100kg, you can only put in the power required to lift that 100kg weight if you have 100kg to push against. So, if the rear tyres have no grip and the front tyres are sticking to the tarmac like superglued leeches then you can lock the Haldex coupling solid, weld it shut if you want, and the torque transmission will be still be 100% to the front, as there is nothing for that torque to do at the rear wheels. Vice versa, if the rear wheels are sat on something super sticky and the front wheels are in free air, then 100% of the torque goes rearward.
The issue is further compounded by dynamic weight transfer. An accelerating vehicle with a centre of gravity above its axle centrelines (i.e. - all cars) will transfer a proportion of its total mass to its rear wheels. Grip at a tyre is proportional to the torque it can transmit without slipping - more grip = more capability to transmit torque. That level of grip increases when you put more weight on the tyre. So an accelerating vehicle might reach the point where the reduction in weight at the front tyres leads the grip to fall below the point at which the torque being transmitted would cause them to slip. In a front drive car you would have wheelspin, in the Haldex car you have a locked mechanical connection that means the rear tyres are doing the lions share of the work. You won't ever see this, since with a locked system the front tyres are revolving at exactly the same speed as the rears, but despite there being a mechanical 50-50 split, the rears will be transmitting more torque because they have more grip and have no exceeded their grip (torque transmission) limitation. This is apportioned torque split, which is highly variable, has nothing to do with clever diffs, and is what really counts to a driver.
Fundamentally though it's still a 50/50 split system until some other external factor comes into play, which really isn't as often as some cynics would have you believe. The slip at the coupling which must occur to reduce torque transmission to the rear axle and thus generate a front bias will only occur when the input torque to the rear axle is greater than the torque reaction from the rear tyres. Until that point, it's fundamentally a locked system. This means that when you are pootling along at a 70mph cruise, and you are using only a fraction of the 300Nm of torque the S3 engine can muster (say - 50Nm) then (gearbox multiplication ratios aside) the front and rear axles are dealing with 25Nm each. A Haldex coupling clutch set to a very low set point can transmit this with no issues and no slip at all, so you can consider it 100% locked and thus set to 50-50.
The system layout brings with it some difficulties in the form of a phenomenon called 'wind-up' that exists in all four wheel drive vehicles with no centre diff or a locked centre diff. To relieve the stresses created in wind-up, the Haldex coupling will allow some slip when rear drive power is not actively required. This slip might amount to only 1 or 2 revolutions of the rear propshaft in a number of miles, so it's not much, but it can be very damaging when not relieved. The way to deal with it is to either open the coupling up regularly, or run it at a set point where the it will slip if the torque transmitted is greater than that determined by the ecu as being the required amount of torque being sent down the propshaft.
So what does this mean with regard to the original question - what difference does comfort-auto-dynamic have on the Quattro system?
Being an active system (forget all that rubbish you've read about the rear wheels only becoming active when the fronts have already started to slip, you're fifteen years out of date and that sort of tech is only used in the R8 now), there are a number of things a programmer can adjust to map the way the system behaves. First, you can run it in a less active mode, where it allows a great deal of slip at the coupling and gives the familiar feeling and stability of afrint drive chassis. You can reduce the ramp rates so that the couplings transition from slip to full locking is nice and steady, and engages almost imperceptibly when required. Whilst this isn't very sporting and won't give the 'feeling' of driving an AWD car, it brings with a number of advantages; it's better for fuel economy, its better for noise and vibration, and its better for tyre wear. You could even go to the extreme that Honda caught a lot of flak for on the old CRV. They fitted AWD to that car because it's what the market demanded, but they didn't want to sacrifice economy, efficiency and weight, so they fitted a system that 'could' drive the rear wheels, but in reality couldn't transmit enough torque to open a jam jar. The punter got the AWD kudos they wanted, which fell apart the minute they got to something slippery and found that even with perfect grip at the rear axle, if the fronts had no grip they were stuck.
On the flip side of the coin, you could set it so that the system achieve full locking very early, allows a greater tolerance for wind up in the transmission, hammers the coupling to full closed at the very millisecond its required to, and runs as much torque through to the rear axle as the engine can throw at it. This more aggressive stance results in feeling much more "Audi", being able to do far sillier things on roundabouts, and of course gives the buyer the sense that he's spent his cash on something discernible. It does use a bit more fuel though, and will result in a bit more noise in the form of clunks and whines. Oh, and all the transmission wind-up forces will be increasingly relieved through tyre slip, which will result in more tyre wear.