1. A method of recognizing textual identifiers within a plurality of words, comprising: at an electronic device, which comprises a digital assistant, having one or more processors and memory storing one or more programs that when executed by the one or more processors cause the electronic device to perform the method: receiving voice input from a user and processing the voice input using natural language processing to produce a textual representation, the textual representation including a plurality of words; identifying, from the textual representation, an actionable intent from among a plurality of actionable intents recognizable by the electronic device, the actionable intent corresponding to tasks that can be performed by the electronic device; identifying a keyword in the textual representation; determining whether one or more words adjacent to the keyword correspond to a textual identifier of a collection of textual identifiers; and wherein, responsive to the identified actionable intent and a determination that the one or more adjacent words correspond to a properly formatted textual identifier, the digital assistant replaces the keyword and the one or more adjacent words with the textual identifier, wherein the textual identifier is a known hashtag or a username, wherein, if the textual identifier is a known hashtag, the collection includes hashtags that were previously identified by a social network, wherein, if the textual identifier is a username, the collection is a set of usernames that are registered in the social network.