[thejeff]

That's a very old thread. At that time the problem was thought to be strictly a problem of version and/or OS differences. I believe the OS differences part of the problem was fixed awhile ago. And soon after reports of the replay bug happening without OS/version differences became more common. It's not clear whether this was a new problem or previous reports were just dismissed as confusion about OS/version differences.

I know I've seen it in SP, with the client and host being the same and thus using the same version/OS & the same mods. I'm not sure I've seen it without mods, but I usually use mods these days so ...

Mismatched mods would be hard to prevent, since they are just text files. I suppose some sort of checksum could be calculated...
OTOH, mod differences aren't necessarily a problem. The display only mods (Banners, etc) can be completely different without changing gameplay at all.