That's beautiful! I have lately been encouraging all my team to take advantages of comments to document the high level business logic as it was at the time of development. It provides utility during code review and future dev, and it's a terrific CYA when debating with stakeholders about what they said they wanted then versus what they "remember" asking for.
That example is particularly verbose because I knew I'd forget it and it wasn't obvious what I was doing. A clear example of something shorter is:
// Briefly the algorithm goes like this:
//
// Slide a 16x16 block across the entire image from left hand corner
// to bottom right hand corner. For each 16x16 block perform a
// discrete cosine transform on it and then quantize the 16x16 block
// using an expanded version of the standard JPEG quantization matrix.
//
// Each quantized DCT transformed is stored in a matrix with one row
// per (x,y) position in the original image (the (x,y) being the upper
// left hand corner of the 16x16 block being examined.
//
// The resulting matrix is lexicographically sorted and then rows that
// match in the matrix are identified. For each pair of matching rows
// (x1,y1) and (x2,y2) the shift vector (x1-x2,y1-y2) (normalized by
// swapping if necessary so that the first value is +ve) is computed
// and for each shift vector a count is kept of the number of times it
// is seen.
//
// Finally the shift vectors with a count > some threshold are
// examined, the corresponding pair of positions in the image are
// found and the 16x16 blocks they represent are highlighted.
//
// Uses the FreeImage library (http://freeimage.sf.net/) to access
// image data
Also as it was interpreted at the time of development - the two should be the same of course but we don't live in a perfect world. If a comment explains exactly what the code is trying to do and why, and the "what" matches the code but doesn't match the client expectations then as well as fixing the code you know you might need to update documentation elsewhere too to make it cleare.
