Cool sites - I like this idea of sharing concepts and getting feedbacks. One other larger one is producthunt.co. I'd be curious to see a full list if you happen to do some more competitive research!
But I have a solution. It's called Indie Developer Club (see my profile for link). All the meetings are small with less than 10 people. You can show off a pre-release demo or talk about the specifics of your project, but you aren't posting it for the world to see. So you get some feedback but you don't have to worry about a competitor Googling you.