If you have more than one address associated with a building the current consensus is to map these as nodes inside the building outline, in the case of a single address there are (some time heated) arguments both ways.
In the end end, because both models are popular (41 million nodes vs 35 million on polygons), any data consumer needs to be able to deal with both, and so really it boils down to a matter of taste and local convention.
Personalty given that the nodes were imported I would leave them like that.