If you want to post feedback, you'd best post it here.

We will NOT read any feedback that is simple, badly written (yep, you better not use "phone language"), short with bad context and the like.
And of course, we will not read any feedback from the comments section.
I'm sure finding this thread is easy enough.

Simply make it laconic, coherent and fit to the context.
For example, instead of "crappy ugly skin", say the flaws, like "it has too much white, maybe some more black will be better" or "I feel it's a bit too reflective, maybe tone it down a bit" and so on.
You don't need to be an expert or have a diploma for anything, if you know a technicism that's good, if not, that's fine, so long as you can describe it well is what matters.