A few months ago while writing a paper, I copied some paragraphs created in one computer to a different computer. I guess the formatting was different. Please see the following image:

I noticed that a strange formatting has also been imported. I thought it would go away when I select all and choose a format. But the problem did not go away. Now, when I am trying to finish the paper, the weird formatting still remains. Does anyone have any solution?

Also, how to make sure that when we copy something from a file with different Styles, we retain the destination style definitions?

EDIT

I would prefer a solution where I do not have to re-do the formatting manually.