It's me that's given you the latest grief then so you'll know where I'm coming from.
I speak now as an artist, a painter, though not a brilliant one. I look on a lot of sites that feature artist's work. Some have watermarks, other's don't and yet, it's usually the ones that don't that are the more famous and best selling artists. Of course, if you want a painting, you want the original, even a print will not suffice so there's no way around that one.
With photographs it's a little different maybe, but ask yourself - if the image size was limited (and on TC it would have to be to fit 256kb) there's no way you could get a decent enough print off it unless it was to fit in the smallest photo frame. Is it really worth spoiling the image by including the watermark? Might be different if they could be copied at 12mps, though.
In fact, could it be considered for POTW or POTY with such an image included? I doubt it.
I'm with Mike, I don't feel that you can concentrate on the overall beauty of the shot when there's a watermark featuring in it.