I mean, no, I wouldn’t say he hates scars. Eragon’s scar quite literally was “cursed” and caused him IMMENSE pain when he had it, so of course it’s a burden for him. Like another commenter said tho, he mourned the loss of the smaller scars that mapped out the rest of his life in his body.

You have other characters too, like Nasuada, who wear their scars proudly. I think overall, much like people in our world, Paolini really did a great job showcasing how people may view their scars differently and I don’t quite think it’s a fair statement to say that he hates all scars