I know I said that I was done contributing to this thread, but I guess I lied.
Thanks for the helpful advice slimfast and the reinforcement trachcoach. You're right. It is dangerous to get caught up in the mentality that lighter always means faster. At some point, it will start to have a nasty backlash and be counterproductive. I guess I just need to figure out where MY optimal racing weight would be. (I can confidently say that I am not cut out to be a 130 lb twig runner, I'd probably just get extremely sick before I even got there.) So I'll just keep eating as healthy as possible and putting in the work and see if my weight sort of just hits a set-point. Also, great distinction between "performance goals" and "weight goals". I think that's a great framework to develop a healthy mentality regarding running fitness and performance.
On a general note, pretty cool that my first thread has generated a ton of responses. Naturally - health, nutrition, and fitness are insanely complex topics that will generate a ton of disagreement. I guess the easy answer is "Well everyone is different, do what works for you, one size doesn't fit all, etc"...but that type of wishy-washy response just isn't any fun now is it?
Also, to the guy who mentioned something about epistemological relativism. Keep in mind that I typed that response in a matter of roughly 20 to 40 seconds. It's sort of funny how you now analyze my words like a lawyer. This is a casual message board with the normal banter one would expect. So I don't know why you're caught up and splitting hairs. In fact, I'll clear it up right now. Nutrition matters. Training matters. Long runs matter. Interval work matters. EVERYTHING MATTERS. I just can't underestimate the importance of really eating clean (unlike Bill Rogers apparently) because the foods I consume really do have a significant effect on how I feel and how I perform.