Manual:$wgHideIdentifiableRedirects

Details
Should MediaWiki attempt to protect user's privacy when doing redirects?

Keep this true if access counts to articles are made public.

This prevents a malicious person from using external resources on their website to cause the victim's web browser to load Special:MyPage -> User:Username, and then looking it up in the page hit statistics in order to correlate IPs from the malicious person's server log, with usernames on wiki.

This setting affects redirecting special pages like "Special:MyPage", "Special:MyTalk", and "Special:MyContributions".