When following an interwiki redirect (e.g. https://wikimediafoundation.org/wiki/User:Krinkle), the target page has a query parameter rdfrom.
This is included (just like any other query parameter is by default) in the canonical url:
<link rel="canonical" href="http://meta.wikimedia.org/wiki/User:Timo_Tijhof_(WMF)?rdfrom=%2F%2Fwikimediafoundation.org%2Fw%2Findex.php%3Ftitle%3DUser%3AKrinkle%26redirect%3Dno" />
For normal redirect, we strip them.
E.g. https://en.wikipedia.org/wiki/Catwalk displays "Runway (fashion)" with a "(Redirected from Catwalk)" message, but outputs:
<link rel="canonical" href="http://en.wikipedia.org/wiki/Runway_(fashion)" />
Removing any trace of the redirect.