Yeah, I understand collecting data is a part of training your model but it could be worth explicitly saying that zero data (either personally identifiable or anonymized meta data or any data at all) will be sold or rented. And if a change to that policy happens, include in the language of the user agreement that it isn't retroactive and only applies to new accounts.

The vague language is what bothers people. Probably having very strong language in the opposite direction (that you will NEVER sell any data, and would shut down rather than sell it) would probably win you favor.