I just started reading tEotW and started watching for some subtle changes in the three boys developments, mostly regarding Mat, when they yells the batlecryes, aproaching Shadar Logoth, (Rand and Perrin yells Manetheren, Manetheren), and Mat yells that other thing in Old Tongue, when they are inside and located in the white building, Rand think Mat seems distanced, or introverted (we don't have Mat's PoV to see what happens but i thought that might be the first subtle change towards something inside Mat) or he just was startled about saying something in old tongue,

i also noticed on the describtion of the dagger, it had snakes carved in on the blade, it is probably noting more then nice carvings on a blade but Mat will have some later experiances with Snakes (and Foxes)