Yes, I remember that thread, and your question was answered there. But once again, the radial expansion of the universe does not in any way imply that photon trajectories are radial. The expansion obeys the cosmological principle, which means that no directions are any different from any other directions, and the photon distribution at every point is isotropic (that means the photons are streaming in all directions at all points, and so collide quite willy nilly if their energies are high enough to make particles). Just look at the CMB that we observe today-- does that look like it's "radially streaming"? (No.) Could that make particles in our living rooms if the energies were high enough? (Yes.) It seems your error stems from the common misconception that the "Big Bang" happened at one particular point, from with all the photons would emanate, when in fact it happened in every direction you look (ergo the CMB), and at every point you can imagine.