System updates send notifications in the same way that comments do. Some users are replying to the system updates. If a user has "Show System Updates" unchecked, they will not find that comment in the feed.
This is a great idea. Too much confusion can arise from this.
Ex: If a user changes the Planned Completion Date on a task they might leave a comment on the system update explaining why the date was changed.
if someone else goes to this updates tab and they accidentally have the "Show System Updates" setting turned off, then they will miss this important information.
This is also a big deal for us if someone uploads a document and then comments on the document, it gets hidden if the system updates are turned off. It would be great to be able to filter out what type of system updates are hidden when that slider is checked.