Files: \NeatPlatesWidgets\ThreatPercentageWidget.lua
\NeatPlatesWidgets\ThreatLineWidget.lua

Text in threat indicator do not display correctly because 'local font = "FONTS\ARHei.ttf"' does not fit for non-latin language.
Maybe you can change it to 'local font = GameFontNormal:GetFont()'

There's no font named "ARHei.ttf" used within the addon, so I just wanted to check if you perhaps meant "arialn.ttf". And in what way does it not 'fit'? Because this font is used for a couple of other things as well.

And while this font will most likely remain the same for latin languages there is definitely the possibility of changing it for others.

yeah, "FONTS\arialn.ttf".
Maybe it exists in clients of all languge.
Fontstring using "FONTS\arialn.ttf" can only display ASCII char.
It doesnot support characters of zhCN,zhTW. When playing in zhcn client, threat indicator always show "????".

Do aura durations work? Or does that also show up as '??'? Because that uses the same font and I find it weird that this issue hasn't been reported before if that font doesn't actually display numbers for zhCN and zhTW.

Duration number works.
Name in threat indicator show up as "???".

I've changed the font used in the latest release so hopefully this should now be resolved.