In any circuit where a transistor or FET is driving a DC relay, its common to see a reverse blocking diode added to suppress the inductive spikes, caused by fast current transitions (particularly the "OFF" transition). Over the years Ive seen such diodes placed across the relay coil, or alternately across Transistor. I don't think I've ever seen both in the same circuit, except in the cases of MOSFETs where a diode is often built in. In my own projects I've used both configurations, and both seem to work equally well for protection. I'm aware that putting the diode across the relay coil will slow down the dropout speed, which could be a problem in some designs. But from a pure spike protection perspective, is one diode placement more optimal than the other?
Almost feel foolish asking this, but I've seen both cases so many times, I have to wonder if there is some confusion or disagreement about it.