Slightly off-topic, but useful as an anecdotal example: This kind of thing is why people prefer Google.
We had search engines with magic symbols prior to Google. People don't like learning magic search language; finding the right shibboleth of qualifiers, excluders, and "near-word" matches feels a lot like doing the search engine's job for it. Most people seem to prefer Google's approach of making a guess at what you want based on past search history.
This doesn't mean DDG can't succeed. But in addition to their selling point of not remembering your search history and having a mechanically-tunable query, they may want to consider offering a search-history "smart" search at some point in the future.