> You are "opting in to sharing your prompts for training", by default in this case.

The English term for that is "opt out" not "opt in." To opt is to choose. If something is on by default, you have not opted in. You were forced in, and turning it off means you must opt out. (I.e., choose to be out.)

normally I wouldn't care about a mistake like this, except that opt in/out are very important concepts in software development and hacker culture. And it reversed the meaning of the original comment in a highly confusing, relevant way.

as another non-native speaker, i think that while the person you're answering to didn't use the default way of expressing this in the english-speaking world, i did understand what they meant, i think they do know what opting means and i think the reasoning is this: when they say data collection is "opt in" by default they mean that by choosing to use a product, you are opting into your data being collected (at the same time). on the other hand, native speakers saying something is "opt out" describes the options or toggles one has available in the default case - when something is toggled "true", you (only) have the choice to toggle it of. so english speakers talk about the controls one has to CHANGE the status quo.

They said "opt in to training on prompts by default," which is coherent English and perfectly fine. The phrases "opt in" and "opt out" will always be contextual based on what is being opted, so it really falls to the reader to pay attention to that context. Please don't give English language advice as though you are an authority; there is not a rule of the English language that would make their usage unacceptable.