Source: https://front-end.social/@fox/110846484782705013

Text in the screenshot from Grammarly says:

We develop data sets to train our algorithms so that we can improve the services we provide to customers like you. We have devoted significant time and resources to developing methods to ensure that these data sets are anonymized and de-identified.

To develop these data sets, we sample snippets of text at random, disassociate them from a user's account, and then use a variety of different methods to strip the text of identifying information (such as identifiers, contact details, addresses, etc.). Only then do we use the snippets to train our algorithms-and the original text is deleted. In other words, we don't store any text in a manner that can be associated with your account or used to identify you or anyone else.

We currently offer a feature that permits customers to opt out of this use for Grammarly Business teams of 500 users or more. Please let me know if you might be interested in a license of this size, and I'II forward your request to the corresponding team.