Thank you for your efforts in updating the excellent tool that is Narvi,
HunterGreen! A truly great addition for the community, able to take into account even the most minute whims of developers!
By default, it follows Michele's ruling above. 11 works like Eye: you cannot spend tengwar on Pierce, and can never get a piercing blow. Favoured by the Grey Wizard is thus a tiny disadvantage, reducing your chances of getting a piercing blow, compared to others who are not so favoured.
In eleven-can-pierce mode, 11 is treated like the 1 that it effectively was. With a lot of tengwar you can still get a piercing blow. Those Favoured by the Grey Wizard work exactly the same as everyone else, and have no advantage nor disadvantage when it comes to getting piercing blows.
The "by default" is the rule as intended. To give you an idea of what "a tiny disadvantage" means, the chance of rolling both a 1 on the Feat Die and at least 3 Tengwars on the Success dice are
0.52 % (i.e. 1 in 200) when rolling
6 dice on the attack roll (and we're only talking about Player-heroes using spears: with bows and swords, you'd need at least 4 Tengwars!), so definitely a disadvantage I wouldn't worry about! For the same reason, the only difference between the "eleven-can-pierce mode" and the "by default" mode is that 0.52 %, a really negligible difference.
In eleven-pierces mode, 11 is treated as 11, so you already have a piercing blow. Favoured by the Grey Wizard significantly increases your rate of piercing blows (by up to 50%!).
That's exactly why we can't allow the 11 to score a Piercing Blow.
Favoured by the Grey Wizard already gives you an average +0.83 on every roll you make (to make a comparison, it's almost like taking
Prowess 3 times, once for each Attribute TN!), so it would be too unbalanced if it also increased your chance of scoring a Piercing Blow.
It is not our part to master all the tides of the world, but to do what is in us for the succour of those years wherein we are set, uprooting the evil in the fields that we know, so that those who live after may have clean earth to till.