  We comment on the derivation of the main equation in the bounded confidence
model of opinion dynamics. In the original work, the equation is derived using
an ad-hoc counting method. We point that the original derivation does contain
some small mistake. The mistake does not have a large qualitative impact, but
it reveals the danger of the ad-hoc counting method. We show how a more
systematic approach, which we call micro to macro, can avoid such mistakes,
without adding any significant complexity.
