I just opted out of forum mail list by clicking at the bottom of an email:
Now, I click on the visit your user preferences link, leading to https://forum.mysite.com/my/preferences resulting in:
Oops! That page doesn’t exist or is private.
@ https://forum.mysite.com/404
If I’m quick, I can see the actual redirect link:
https://forum.mysite.com/u/%C3%83%C2%AD42-Xblade/preferences
This seems to be a Unicode issue. I have enabled Unicode on my site. Use this example:
í42-Xblade
Notice the accented í .
I could guess that this is not the only link that breaks due to Unicode names.