> It’s mostly for me and friends I know personally – nothing like the bigger, public ones.

I'd agree with you if it had thousands of users, but not when the user count is 8. If you have 8 users on your SMTP server, damn easy to know with certainty if any of them did anything that might be considered malicious.

Mastodon, perhaps unwisely, replicates all media it encounters.

Again, it's eight users, one of which has full control over the database plus an approximate timestamp when something went wrong.

Super easy to check every outbound click, every post published, every post received... Everything.

I run a single user instance, and I definitely can't review every post received?

Well that's... terrifying.

In reality, it barely makes a difference if you want to avoid hotlinking (and that has other bad privacy privacy implications, now all your users load bad content).

Law enforcement makes no difference between proxying, caching and storing indefinitely. At least not during all the steps that precede your hardware being seized.

Is illegal content relevant to phishing warnings?

So is google drive.