I think it's important to graphically illustrate how DDG's search results correspond to query strings (e.g. priority relations, sequential association and so forth), at least to give users some confidence about whether they've done the best they can -- if not for the community! I've had several ideas to improve queries; but without a baseline understanding about DDG, I haven't been able to reify them. How can I learn more?
For example: interative search refinement to progressively filter through search results. Does this really make any sense to provide? There's likely a few (if not many) aspects in which it does, but I'm sure you try the best you can to support this within single queries.
Next, consider a state-preserving hierarchy so users can experimentally browse through their query constructions with ease.