Issue with permanent highlight

Hi,

I opened an old document and there is a whole paragraph highlighted in blue - no idea why -, and no matter what I do it sticks. I got around it simply by deleting the thing and striping the formatting from the text by copying it into google, but that could hardly be the intended way of dealing with this stuff.

So how to get rid of the blue highlight properly, provided it is a feature and not a bug?

Obviously setting the highlight on none does not work.

In the link I enclose the example file suffering from the same issue - I copied (ctr+c ctrl+v) the problem over.

thx