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With query expansion mode returns some odd results?

This mode guesses what the searcher was after from words MySQL thinks are
related to the terms searched for. If your content implies an association
between two otherwise unrelated terms then MySQL will make an assumption
that they are related. For example if you mention Ducks and Strawberries
together in a few post your index will see a relationship and searches for
Ducks may return results for Strawberries.