Strange I always invert phase of kick and bottom snare BEFORE mic placement. Thought that would be technicaly correct because when you hit the top head of a drum with the drum stick the very first thng happen in the top mic is the diaphragm is sucked outwards. The same hit causes the bottom mic's diaphragm to be pushed inwards. So you get 2 waveforms with one starting downwards and one starting up.
by flipping phase you get the 2 waveforms starting in the same direction.
This was told to me some while ago. Maybe the one who told me that was an idiot
However I'm with you. In the mix do whatever sounds right.
Sorry for the bad english! Hope you got my point!