I'm not saying that yet, just that this looks like an encoding issue -- something I have a bit of experience with -- and that if this ticket was assigned to me I'd start with checking how the PHP script imports and parses XML files before saving them to the database. Could be an XML declaration that needs adjusting in the post-in-thread-context view (vs. isolated view) or it could be something entirely different. Not really a Windows/Mac issue in the way most people think about it but specifically how display fonts translate across platforms and browsers.