1. A method for improving a machine translation engine by augmenting the machine translation engine with preferred translations, the method comprising: receiving indications of content items that are machine translations of source content items, wherein each content item is associated with a user score; identifying, as low scoring content items, the content items that are associated with a user score below a content item threshold; dividing the low scoring content items into multiple n-grams; computing an overall score for one of more n-grams of the multiple n-grams; selecting, as low scoring n-grams, at least one of the one or more n-grams that has an overall score below an n-gram score threshold; obtaining preferred translations for each of the selected low scoring n-grams, wherein each preferred translation comprises a source phrase in a first language and a translation of the source phrase in a second language; and augmenting the machine translation engine by one or both of: including the preferred translations in training data used to generate the machine translation engine; or configuring the machine translation engine to, when performing a translation of an item, identify when a preferred translation matches a phrase in the item by matching the source phrases of the preferred translations to phrases in the item, and, when an identified preferred translation matches a phrase in the item, use the translation of the source phrase in that preferred translation instead of results that would otherwise be generated by the machine translation engine.