The most common requirement for formatting a text is the ability to insert a new line in the resulting document. Putting the text in the new line in comment doesn't help. For example, HTML ignores new line in its source text and continues to display the text on the same line. It only inserts one space before this text.
You can use <para> tag in your XML comments to start new paragraph. This is the preferred method because the <para> tag is an official XML comment tag. Alternatively, you can use <br> tag for a line break.