Mastodon server admins can now help spread the word about Mastodon by activating their server's link referrers. It just takes one small change in the settings, and will let clicked sites know that your server is the source of their clicks (but no other info is sent).
I've done a guide to this which explains how to activate referrers, and the reasons why a server might (or might not) want to activate them:
As always, let me know if there are mistakes 