None. All the information generated by the Leaner Coffee Power-Up (votes, voters, discussion durations) is either stored in the Trello cards to which it's related or in the Trello board itself. It never leaves your board.
There is no commercial objective behind this power-up, so we have no need to collect information for any kind of business purpose.
We did consider collecting usage information (e.g. which Power-Up buttons were clicked), to analyse user behaviour and improve the product, typically by tweaking or removing features. However, we do not do any such thing at this stage.
It is possible, of course, that the current state of affairs with regard to information collection will change in the future.
If that happens, we will update the README in the Power-Up's repository, and attempt to notify existing users.
Please note that we can only notify users while they are on a Trello board with our Power-Up enabled - since we do not collect user data (such as e-mails), we have no other means of communication at our disposal.
If you have any questions or concerns regarding this policy, feel free to contact us at leanercoffee@tatablack.net.