It's not a proofreading mark - I think it's a fixed-width or maybe a non-breaking space.
By the way - although I don't think it would make any difference to your current situation - it's always best to use File>Place rather than copy and pasting to get text from Word into Indesign. It gives you better control.
Non-breaking space. Interesting that there seems not to be text ahead of it. Right-aligned paragraph perhaps?