Maybe I shouldn't be one of the first to respond but I have nothing better to do right now! These are great questions.
1. Do you think limitation is a reason you do chip?
Yes, it is not the only reason but it is a big reason.
2. Do you feel like the limitations of your chip music is any different to the limitations imposed by other platforms (they all have them)
Certainly. Having 16 patterns, for example, is very different from using a tracker that can extend indefinitely, while having 6 voices is certainly easier than having just 4 channels.
3. Why do you want to work within these limitations? or, do you feel the limitations are an influence in your choice to work at all?
Only because it is a challenge. To be honest, I use the software because I like the sounds I can make with it. I'm willing to overcome the limitations, and would probably enjoy not having those limitations at all, but I do like the challenge and feel proud of myself when I come up with interesting ways to overcome those limitations.
4. What is it about the specific limitations imposed upon you have any effect on your output?
My music can tend to be repetitive because I often have to repeat patterns to have a song longer than 3 minutes on just 16 patterns.
5. Does "confronting limitation" justify lesser quality as a "proof of concept"?
I think in this case you need to define "justify." I think it certainly does, but I would never pay for a song that is lower quality & only a proof of concept. I might give the artist some kudos for accomplishing what they did with this song, but I won't listen to it again. I only listen to songs I genuinely enjoy. So a song being a "proof of concept" would not be a reason for me to buy it.
* p.s. I should qualify what I've said here with this: I have yet to actually put any of my DS10 songs for sale. So far, all the stuff I've released has been "proof of concept." But I am working on some stuff right now that I consider "good music" regardless of the limitations of the platform.