The file appears to work as normal for me so there isn't anything special about it in terms of selecting text. There isn't any content controls and I can't see any reason why selection would work differently on your machine.

I assume you have the same issue with all documents, not just this one. It sounds like it is just a colour shading on selection that you are not seeing rather than any broken functionality. If that is the case, perhaps it is a Windows setting rather than something in Word. I would go and change the Windows Theme settings to see there is a setting there which resolves the issue. You get into this by right clicking on the empty desktop and choosing to Personalise.

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Andrew Lockton
Chrysalis Design, Melbourne Australia