The closing quote of the message merges into the URL inserted with variable $2 thus breaking the link, e.g.
"NewUser" has requested an account and is waiting for confirmation.
The email address has been confirmed. You can confirm the request here "http://www.example.org/Special:ConfirmAccounts".
I have inserted <> into the message for better comprehension. I guess quoting the URL should be done with <...> anyway if at all necessary.
Version: unspecified
Severity: normal