When we tested OJS (2.2.4.) for our journal, we noticed that non ASCII characters in people's names weren't displayed correctly virtually in any e-mail client.
I have a patch that mime encodes name part of all e-mail fields (From, To, Cc and Bcc), not just the Subject, using String::encode_mime_header function.
The patch has been tested on our production system (we'll register soon), and I'll be happy to provide it, as soon as my two posts are cleared.
Although the patch is against 2.2.4 version, I think it should apply cleanly on the current head since as far as I can see classes/mail/Main.inc.php hasn't changed.
EDIT: Patch attached!