I think Ralph summarized it very well. My thoughts on the topic are very much the same. Before no one comments on a MOC I posted, because nobody likes it I'd rather get constructive critism on how to improve it or why it is bad as just get no feedback at all. I'm doing LEGO as a hobby for only three years now (I did not have any LEGO in my childhood). The first real MOC I build must be about two years ago. I think my creations have improved a lot since then, but I'd still call me a 'beginner' and would be thankful for any tip and hint to improve my building skills.
A special code or phrase in the topic title or initial post might be a good idea, to encourage everybody to give you this feedback.
An index of building techniques sounds like a good idea. The questions how to group things in such an index so you can easily find it.