My comment referred to the typical Markov chain type word prediction, which is the mechanism behind the 'sentence context' you referred to in those custom IMEs.

My comment referred to the typical Markov chain type word prediction, which is the mechanism behind the 'sentence context' you referred to in those custom IMEs. What I described is basically taking that mechanism and baking it into the standard OS without all the custom personalization options the IMEs offer and just offer a ready to use "English + OtherLang" option. I don't think iOS does anything like that, but there you can still reduce the threshold at which you'll auto-correct and get a significant improvement. Just goes to show that on all platforms there are still plenty of trade-offs to be explored.