On the behalf of your mentioned problem. I don’t know if it still holds as the eu’s digital market act now forces “gatekeeper” messaging apps to open their api.
At least under the gdpr in europe it should be a privacy violation as you need to have the consent of the user to process it’s data. So they would have to go to every single one in a comment and ask for permission if they want to use it for recommendations algos or check out if contents fits advertisement.
Die erste gute Idee der AfD. Ich bin überascht dies zu sagen ¯\_(ツ)_/¯