There needs to be a way to completely and permanently disable all spelling correction, stemming, synonyms, suggestions, and so forth -- something like Google's "Verbatim" sense, only better because it would actually work and could be made the default. There may be reasons why I'm searching on a misspelled word or bizarre phrase, and it's extremely annoying when the search engine "corrects" my search for me. Just return the %$(*@%^ results for my search terms, thank you!
And no, enclosing the word or phrase in quotation marks does not always work. In fact, I'd say it works less than half the time. It also seems to ignore punctuation, which may also be part of my search (for example, searching for a particular file, including its extension).
Frankly, I hate all search corrections and suggestions. I think they're just another symptom of the dumbing down of society. It's search for idiots who can't spell and don't know to identify the salient keywords in an idea to search on them. If you must lower the bar to embrace idiots, at least provide a way for those of us who aren't illiterates to shuck off the training wheels, search intelligently, and receive unfiltered results for what we actually searched on. Maybe a dedicated subdomain like "notstupid.duckduckgo.com" would work.