Is it permissible to perform the regular Sunnah prayers in congregation, and how does one respond to those who say that this was not established from the Prophet, peace and blessings be upon him, and that it is not permissible to make an analogy to performing Qiyam al-Layl in congregation?

The fundamental principle concerning supererogatory sunnah prayers is that they are to be performed individually. It has not been authentically reported that the Prophet (peace be upon him) or his Companions ever prayed them in congregation. Emulating him (peace be upon him) involves following both his actions and his omissions. It is permissible to perform them in congregation occasionally for an incidental reason, such as teaching a new convert to Islam. However, consistently performing them in congregation is a reprehensible innovation (bid‘ah makruhah), as neither the Prophet (peace be upon him) nor his Companions regularly did so.