Like HN, Forrst is full of people who are earnest and invested in their behavior there. It doesn't mean everybody is always right or perfectly behaved, but they are sincere and really care about the topics at hand. I also like how Forrst users particpate when they have something of value to offer, rather than just to hear themselves type. (that's one thing that bothers me about Quora: people speak up without any really compelling reason to. Compare to HN when most skip threads if we're just going to repeat something.) Forrst also has excellent design and that permeates the culture and people treat design both as a craft and a technical skill.
The only thing I don't like about Forrst is probably just me: they have some etiquette guidelines i don't totally get. You can show work that's in progress, but i once saw a guy show a fully completed piece of work that a moderator thought was too self-promote-y. Then I once got modded because I showed some industrial (non digital) design ( because it wasn't graphic, though featured graphic typography on a sign). It's possible this policy has evolved OR I just didn't read the fine print closely enough, but i felt confused.
I would encourage you to check it out.