what is the vi you are using ?
wrting string to a text file will simply save data as pure text, ascii characters, without formatting.
what you are trying to save is formatted on the screen, but when saved to a text file, all the formating (italic, bold, etc ) is lost.
If you want to save formmatted text, you have to use a word processor, like word pad. you can have LabView thru active X save formatted text with word pad.
notepad is a pure text editor