Do people chat the same way they speak? My experiences with IRC have been that a lot of people speak in an abridged way to limit the amount they have to type. (I always type full sentences but I seem to be in the minority.)
But what about some kind of chatbot app that you talk to with your voice? iOS has a built-in speech transcription API. You could record the user’s speech, transcribe on-device and then upload both speech and transcription for users to validate just as they do now.
I’ve been doing experiments training DeepSpeech on data that was transcribed via Google’s API and the results have been pretty good. It seems to almost always get words in frequent usage and only stumbles on obscure words or unusual names.