If the damage will not affect the resale value if you ever want to get rid of it then live with it,D.
You can be 100% certain that the damage will affect the re-sale value. Owners of high-end refractors are generally finicky, if not OCD.
That is the one thing we can be sure of..
How much it affects the view.. who really knows, I might be extra happy with the view because I got an A-P Traveler for $3500 rather than the more normal $5000+ whereas the next guy might always be thinking about that scratch and just can't let it go..
When I bought my 25 inch Obsession, I got it for a very good price because it had a clamshell fracture on the backside of the mirror. Whether or not it affected the views.. well the views were very good but it always bothered me. When I went to sell it, I prominently displayed the clamshell and asked a price in accordance with the perceived loss of value.
As it happened, the eventual buyer for the scope contacted me at the very moment I had made the deal for a 25 inch F/5 Nova mirror and Obsession upper cage that showed up on Craigslist.. The seller was asking $500, I gave her $1000 and sold it to the eventual buyer for the $1000..
Now refractor people are much more likely to suffer from OCD than reflector people but in the final analysis it's all about perceived value and a fine lens that scratched, it's got to affect the perceived value..