Thanks Koonschi, I'm sure that will be quite helpful.
In the meantime, we've tried the following things to work around this issue but they did not work, we did find another "workaround" of sorts, that does work, but it is messy.
Don't work:
Copy / Paste
On-Screen Keyboard changed to different language keyboard (some special characters work this way, but not all)
Using CTRL codes to create special character (Idendified CTRL codes using charmap.exe)
Using macro software to "playback" the characters
None of these workaround options worked.
We then tried a few other workarounds regarding changing the player name.
We tried changing the "playerName" in the settings.ini, but it keeps getting reverted every time we start the game.
We tried changing the player's steam profile name, and that worked in chat, and several other places, but when you press F1, you still see the old player name.
I theorized that this was tied to the characters data file, which is probably bound to a steamID, or some other unique identifier, not the Player Name, so it was not being recognized everywhere. We then went ahead and deleted the player files in the saved game folder to test, and sure enough the player name is registered as the new steam profile name.
I think this is the only known workaround for this issue at this time. Now all we have to do is revert the save, transfer all his stuff to me, then delete his player data, and we SHOULD be okay.
Fingers crossed.