I've spent the last few days trying to track this down, because I hate to just default to forums. But I'm hoping someone can help me.
I created a plugin that auths against a third party user store, and that works just fine. However, I have one or two posts that have a special character in the slug, α, and you can permalink to those posts and everything just fine.
However, my plugin has its own login page that posts to wp_login.php with the username and password and preserves the last page the user was looking at in the redirect_to url parameter. When they enter their credentials, and post back to the form, on success wp_login redirects to a page that doesn't have the special character in the URL so I get a 404. It must be sanitizing the URL, but I'm wondering if I can convert it to something else before passing back to the system so I won't get the 404. I tried using htmlentities(), but I still get redirected to a URL with the α character missing and get a 404.
Can someone help me figure out how I can preserve the special characters, or convert them into something else that the system can process without being stripped off?