One refinement suggested by my initial version of Table View was to restrict the number of versions for comparison to some subset of those available. This has the advantage of further improving the signal to noise ratio, and does so in a purely digital way.
To help the user select a subset of versions intuitively I used a dropdown menu with the selected versions marked by a × sign. (A tick mark can't be used because browsers already mark the currently selected item with a tick). This method is very compact. It always occupies the same space however many versions there are – something not achieved by the usual technique of a set of check boxes: