Hear, hear Cees and Jack. Some very obvious flaws (and serious for a buyer) pass uncommented, yet filler posts abound along with unimportant drivel.
That said it is the BaT listing details themselves that are of interest to us (rather than the comments section, or even the auction.) The listings always have a VIN (mostly correct) and most often the mileage. For an owner looking to find W113s of close serial #, the BaT listings are a decent source of relevant pictures - and some of the professional listings of pristine vehicles give a virtual reference set of images.
I believe we should look to capture as much of this information for our reference purposes. It could be a separate table/wiki from the Registry of members cars and its purpose should be to glean details of W113s from whatever source, and permit links to that source (eg BaT, Hemmings, etc.)
Further it may be of use and entertainment to have a separate forum dedicated to market color and commentary, as Jack proposes.