The background of the rightmost column of the editor shows different colors if this property is enabled.
You can enable and disable this setting via settings notebook - General.
A Softreturn disappears if the formatting gets different. If you change the window size and you edit an unformatted file, the editor let appear and disappear Soft Returns.
A Breakreturn also disappears if the formatting gets different. In comparison to the Softreturn which is always related to a space character, the Breakreturn can occur everywhere. But appears only if a long line has got no spaces.
In the "special functions" menubar item, you will find commands where you can transform
text with Softreturns into text with Hardreturns and reverse.