Re: Repair or discard?
"However, a buddy of mine insists that the line's castability/floatability is compromised and that I should just get a new line."
Just my .02 cents, but the answer is 'yes.' Regardless of the line core, if crunched, they will take in water. For your fishing this may make little, or no difference. In many situations it makes a hell of a difference. Minor tip damage you could re-seal and it will work for some period of time before it blows off, and then you're back to square one.
"We sleep soundly in our beds because rough men stand ready in the night to visit violence on those who would do us harm." – Winston Churchill