Your comments

At the moment, as the site is growing rapidly, that can be useful for finding people who are migrating from other sites. I think at least 80% of the people I'm following I only know have accounts on FurryNetwork due to the activity feed.

A (temporary?) workaround for this would be an option to hide those messages from the activity feed, much in the same way the what's new page can be filtered on art, stories, and so on. This would make the activity feed more useful and versatile. It just wouldn't directly solve the stalking issue in the parent post.

Unless the site is redesigned in a way that hides that information from EVERYONE by default and only makes it visible to people you explicitly authorize, the features you want won't actually accomplish anything at all. Even if you don't explicitly approve the user as a friend, anyone can go to your page and see your activity whether they're watching you or not. Blocking them won't help either as, at the moment, your profile and activity on general-rated submissions is still visible to logged out users.

I do understand a need for privacy, but it would require significant changes to the site's systems to facilitate this.

I just posted that as a separate idea, though implementing that might also solve this issue. Specifically, if imported submissions take the original timestamp, then the site can just sort on time and everything works.

Seconded. There needs to be something that doesn't delete EVERYTHING, but is significantly faster than simply dismissing entries one by one. A way to delete everything currently visible (that is, not filtered out) or to directly delete all notification of a certain would be ideal.

As a specific use case: I usually dismiss journal posts without reading them unless they're recent and have a good title, so a way to dismiss all those without dismissing art by the user would be helpful for that workflow.

I'd say it should be opt in rather than opt out, but otherwise this isn't a bad idea. It would also help keep up when you're eagerly waiting for that exact moment when an artist opens for commissions.

This is probably especially useful for authors. Since SoFurry handles all stories natively (unlike FA supporting a few file formats and Weasyl allowing Google Document embedding) it may be easier to import content from there than trying to adapt how those other sites handle text uploads to the format supported on FN.