(All?) WMF teams organize their work in sprints which means that at the start of one, all tasks get added to #Project-sprint-4711, perhaps moved around in that sprint's columns, etc. This information is mostly interesting for the people involved in the sprint, but for outsiders it's not relevant if a team met their plans, but if work was done and/or the task was resolved (or declined or …).
It would be nice to ignore such sprint-related actions on Maniphest tasks. The Email Preferences only allow to ignore all project changes or all column moves of a task, and if you choose that option, even changes in projects that you are watching are ignored.
There should be an option that actions related to sprint projects (IIUC "Is Sprint" = "Yes") are ignored if you are not a member of the (sprint) project.