Re: rolled-up sleeves
I see other students do it all the time. I have never done it though because I prefer long sleeves. In fact, I usually only seen it done with the thinner GI, and not so much with the thicker Judo style Gi.
As for injury, I went to a Donavin Waite seminar with a kidney injury. Afterwards, I was told that rolling up sleeves was not the way to indicate injury, but a red cloth tucked into my dogi pants was. I have never seen that before and was taken back when a Sempai mentioned it was common practice.