and silk was considerd arrowproof because the arrow couldnt rip it, so the arrow pushed the cloth into the wound, preventing most infection and removing the arrow more easily, but you have to take into account the numerous layers of armour (as you do by moving onto mail etc). Never the less, just getting a bad scratch in combat could and often did lead to a deadly infaction which, if not killing you, would cause a limb amputation, whos more likely to recive such a wound - ninja.
armour was also shaped and curved to prevent people from simply stabbing through their armour via deflection, or there wouldnt have been much point to it, thats why crossbows were more deadly than bows because the crossbow was closer range like a sniper.

if youve been tought PROPER sheild fighting, then you will know hoe bloody hard it is to fight someone who knows what they are doing with a sheild, and that on it's own, let alone fully armoured would stump a ninja (unless they had ninja magic lol) as for parrying, you can parry and block with ANY type of sword, but oriental swords being one sided are a hinderance, and the curve is even more of a letdown. BUT alot of people today, are tought compleate rubbish about how to fight, so EVERYONE is relient on actually learning something decent lol

i agree totally with you about valor and chivalry. I have had countless people who turnup and before they have even held a real sword they want to stab people in the back, once they become experianced in only a week, they can see how stupid this was, most people who stab in the back get hurt because a decent swordfighter learns to "sense" everything around them and will often turn around and hit you by accident. Backstabbing is a very VERY difficult technique to learn to do properly.

if you need to stab in the back it means one simple thing, you lack any ability whatso ever and your still gonna die. And your probably gonna die worse than an honest opponant.