In the Updates section, on the top right-hand side, there is the following…
If you disable this, it will hide those system updates, like when someone logged time to a task, when someone uploaded a document, when the project status changed, etc. It is 'sticky' so if you had disabled it on a project and then navigate to another project, it is still disabled (until you turn it back on again). Terry Hynd EBSCO Information Services