That other guy said something like 'its out of character' or 'it takes a lot of concentration' but there motivated, so they'll perform to the best of their ability
(1) Not only when accelerating, but also while moving at constant velocity.
(2) The "very little" (sic) energy equals, in fact, infinite energy according to the formula for relativistic kinetic energy at lightspeed.
(3) We are talking about the Flashes moving through air, not moving through solid rock.
(4) Nope. Air CANNOT be compressed into solid phase at normal temperatures. The critical temperature of air is 132.41 K. Thunderclap is a shock front of compressed gaseous air, NOT a solid wall.
(5) No, it's not. The Speedforce protects Flashes from air friction. They experience regularly, while moving at lightspeed, a stream of much more energetic air molecules (mainly nitrogen and oxygen gas) in much larger amounts than what is present in a "thunderclap".
when you run into a still object you will suffer a force equal to the one you imprint on it. if the object is running towards you at the same time, you add the vectorial forces. the flashes' are the ones whose energy approaches infinite, not the air resisting them. if a compressed wall of air is accelerated towards them at the same time it will hit much harder. So:
a) your entire argument is a no limits fallacy that their aura can dissipate any amount of energy whatsoever provided it's a mechanical wave traveling though air.
b) you assume the thunderclap pales in comparison to their acceleration, but if that were true, then IMPs would be clearly more powerful than it, when the hulk's thunderclap feats can actually rival perhaps even surpass IMP feats (notice that IMP is really just a name, their mass is clearly not infinite). example: doing the rulk in at his peak.
in marvel it can and the air doesnt solidify by losing energy and forming chemical bonds (quick compression would actually make it hotter). the air molecules are forced together so that the air mass's volume shrinks like it would if it were solid. it becomes as dense as a fast traveling solid and hits just like a moving wall.
Yes, it is.
Nope. You do have some correct stuff in there, but it is mixed with errors. According to the principle of relativity, there's no absolute frame of reference for motion, there's only relative motion. If you run at a stationary wall at velocity v, the effect is exactly the same as if you were stationary and the wall came to you at velocity v (assuming the system only consists of you and the wall).
The Speedforce can already deflect and dissipate the ultimate case: the air flow hitting Flash at lightspeed, with infinite energy and momentum density (whenever he's running at c).
I'd like to also remind you about the relativistic addition of velocities. The additivity breaks down upon approaching the speed of light: in Flash's frame, the thunderclap shockwave cannot approach him faster than c, even if he's running at c.
No, even in Marvel it cannot, unless you can prove otherwise (with a scan). Of course the air pressure and density are considerably higher within the shockwave generated by the thunderclap, than in the surrounding air, but the air still remains gaseous. When the Flash runs at lightspeed within the atmospere, the atmosphere along the path is compressed into a thin layer of infinite density anyways (relativistic length contraction), containing much higher amount of substance than the thunderclap. The thunderclap shockwave contains just the small volume of air which was displaced by the brick's hands.