IMHO the only reason for the knowledge of a previous owner making any difference to the price is very simple ...
If it was known that the previous owner was a bodger, didn't care for the car, drove stupidly, wouldn't spend a penny more than he had to .... the value would decrease as the car would be at greater risk of failure.
If it was known that the previous owner was a competent mechanic, spent many hours caring for the car, drove within the cars limits, spent what was needed to keep the car as best as posible..... the value would rise as the car is at a reduced risk of failure.
The ONLY element of personality therefore that enters the argument is how he cared for the car .. not if he was nice or nasty, generous or tight, etc etc.....
However I can understand folks questioning the second of the above two statements IF they are unsure of his honesty.... for any reason.... they could legitimately question if the reported work/care was actually done or just talked about.
That then leads to you being the seller .. not him .. and how you back up any claims made by him in the past ...and the question is then one of your honesty, which IMHO is beyond reproach.
Thus within the forum I would suggest it's value is slightly increased by its provenance, but outside the forum it matters not a jot ...
