Reorg shows up in the debug output immediately in the client

It's absurdly easy to detect (just look for a chain that's been reliably mined for 6 blocks/1 h and then at 1 h the 7 block fork is detected --> report this to user via pop up)

The likelihood of two totally different chains size max of 6 MB (6 blocks) existing on the network at the same time and both being reported to a vast number of different nodes with neither group of nodes interacting is really, really unlikely