I will rewrite the following description as needed.
Under the History tab of every page, there is a list of revisions of the page containing details of the timestamp when the edit was made and the user who made the edits. Next to each revision (if the revision is not by the current logged in user), there is a 'thank' link. Clicking on this link will send an notification to the corresponding user using the Echo extension, unless the user has opted out of receiving thanks notifications. (Anons can't currently receive thanks, so a simple version of User.thanks_enabled property, as mentioned in Subtask 4, is needed here) .The Thanks API is called using action=thank, with parameters rev, source and token. This concept of thanking revisions, as seen in the class ApiRevThank (which extends ApiThank) in Thanks needs to be implemented in Pywikibot, and then tested using the test suite.