We built something similar around 2008 and maintained it for a couple of years. Ultimately, we chose to shut it down, due to the difficulty in getting good discussion, and the amount of "pseudo-spam" from folks who would flood us with links to crap and designer link-bait.
My suggestion is to ignore the design feedback you're getting here. It's not that it isn't perhaps accurate; it's just not your biggest concern.
In my opinion, the real key with these communities is the discussion. HN is ugly, but the content is good. Additionally, the active nature of the community is huge. Part of that has to do with it having first-move advantage; the other may be the associated "carrot" of pg looking at contributor involvement, come application time.
My hunch is that the biggest part of why HN is so active relates to startup-folk being more concerned with the data/insight than presentation. I could be entirely incorrect on this point, but my feeling is that the majority of designers simply aren't geared the same way. They're more interested in seeing eye-candy than reading, thinking, and discussing.
This is a generalization, and there are certainly designers who are geared quite differently. (Personally, I find sites like dribbble really boring, but am on HN within 5 minutes of waking.)
The challenge here, for you will be in getting a sufficient mass of good contributors/commenters (i.e. Thoughtful, meaningful dialogue). I think it's will be hard to make this happen. I do hope you'll prove me wrong, though, as the design community could use something like this.