You can use the Propneut extension without registering as a user. So, for using Propneut to get access to posted alternatives, you do not need to register any data with us at all.
However, if you want to post links using the extension, or if you want to participate in editing posted links, you need to register as a user. The reason for the need to register is so that we have the option to block users from posting or editing links if they are 'misusing their trust'. We dont have any written terms of use, so 'misusing their trust' will generally mean any type of obvious 'misuse', like posting spam.

When registering an account the only personal information you need to supply is a valid email-address. The reason for registering a valid email is to enable us to send you a new password in case you forget it. For this reason, you can not register two different users with the same email.

The email you registered is not used for any other purpose. The email is stored in our database, but is never given away or shared with others.

Other that storing a valid email address that we can contact you on, we don not store or use any other personal information.