I try and comment on as many as I can, but will admit I haven't been doing it very long. I'm a funny sod, I am (in case you didn't already know that) and thought it was a bit showy of the people who did it (I was brought up to think showing my own work was attention seeking and the suchlike). I've recently changed my view on that and seen the error of that, the massive error, as I've found, when I have done it with mine, no-one made me feel like that at all. I was given quite a bit of help in improving a couple of them, to be honest, and I'd never have got that had I not done it. It was teachers at school that made me feel like that, not my dad, but it stuck, and stuck for far too long.