Danne,
The term 'scary sharp' came from the Old Tools site. Twenty some years back there was a thread on sharpening, everything from using an old flat rock to diamond stones and water stones, even finishing with buffing.
We regard tools with some reverence even, and 'scary sharp' means properly sharp if you will. There is some limit to just how sharp a tool should be to be useful, and also some limit on how dull we should work before sharpening. I don't know the list population as of today but it is a good number of folks. Some of the 'scary sharp' stuff involves working with graded abrasive papers on a backing plate, whether an old chunk of granite or a plate glass chunk. Down to 2000 grit with just those papers I can shave my forearm easily. Stroping, as we do with head knives, applies to wood working tools as well, from a pocket whittling knife to the finest compound curves on a molding plane blade.