Early in December 2012 there were three attacks on Shia Muslims in Afghanistan, which did not get a mention here IIRC; catching up on my reading I find Ahmed Rashid has written:
Al-Qa’eda in Afghanistan is trying to repeat the formula it used in Iraq: sectarian war as a tool to divide the country, defeat the American occupation and undermine Iranian influence. By killing Shia and prompting a backlash against Sunnis, al-Qa’eda was willing to plunge a majority Shia Arab country — which had never known sectarian killings — into mayhem. It was chillingly successful in its aim.
He ends with:
But those who want to destroy any hope of reconciliation between the Afghan government and the Taleban before western forces withdraw in 2014 seem now seem to believe that sectarian warfare, and the bloodbath it brings, is their last hope.

Given the Taleban are a "wide church" regarding their adherence to Islam, with a steadily growing conservative element, I do wonder if these attacks were AQ's.

Nor am I persuaded that GIRoA and the Taleban are likely to be reconciled.

Is it possible that within the Taleban coalition a group which is anti-Shia, as some are along the Durand Line, was responsible?

As Jason Burke remarked recently regarding the complexities of Afghanistan, he illustrated his point citing a group of Shia Hazara fighters fulfilling an obligation to a Sunni Taliban leader fighting near Kabul, before 2001.