Mods are indeed a strange thing. We all seem to like doing a few bits but when it comes to buying, everyone wants to buy a standard car. I personally would be put off at a dealer, but if I was buying privately and could meet the person selling then I think it would be less of an issue.
However, I did buy my Ducati knowing it had a few mods on which seemed ok. I actually didn't realise how much stuff the previous owner had done but it really sets it apart from other similar bikes and looks a lot better for parts that have been added. Even the Ducati dealer hadn't listed half the stuff on the advert.