You may have to get more specific about your problem. From your post and screenie one would assume that it's the highlighted selection giving you trouble ...
Highlight (select) text, Delete and then Undo -
Undo just Undos the last action - the Delete, not the highlight. So you Undo the delete and you see what was unDeleted (it is highlighted).
Now we come to a trouble spot for me. In that screenie is that highlight your selection?
If it is how are you able to get a 'block' selection without the entire line being selected?
There have been times where I'd give anything to do a block selection like that.