What are the limitations? Can pictures be posted? Codes? Links? I didn't quite understood the 'moderation powers' part. From an moderator PoV, it is kind of important to 'guard' everything.
To be honest, it isn't dramatic if someone posts the same question twice unless it is clearly explained in the tutorials.
I don't know about pictures, but code and links would definitely be possible. However, remember this is an open source project that I can modify to my own discretion so any missing features that people feel are needed, I can try to add in. I'm definitely more experienced as a web developer than when I first made BulletForge (honestly, that was a practice thing, but I'm confident now) so there should be less problems.
About the moderation powers thing. How it works is that every new users starts with the ability to ask questions, give answers, and vote up. As their contributions are voted up by other people, they get reputation points. As you gain more reputation points, you gain the ability to do things like leave comments on answers, vote questions/answers down, flag things as spam, and close/reopen your own questions. As you get massive amounts of reputation, you'll even get the ability to edit tags for questions, edit other people's posts, vote to close/reopen other people's questions and delete closed questions. Towards the very end, if you're really into it, you'll even automatically be granted some moderation powers.
If you're worried about people messing things up, keep in mind that they have to be helpful for a pretty long period of time before they're allowed to do any real damage. The most damage new users can do is spam stupid questions or give bad answers, which can be cleaned up by more senior members of the website. It's not worth the effort for most trolls to spend that much effort before ruining a site. Worst case scenario, a real moderator or admin can remove a user and revert his harmful changes and he'd be back at square one with no reputation again.
