From MTG Wiki
Paragraph styles are defined in each template. The art department controls templates and styles.
The menu on the left side of the Multi-Channel Text Editor provides several options of pre-defined styles for a range of situations.
As the name implies, these styles are applied only to selected characters. This is the proper way to bold and italicize copy.
To apply a character style
Select the copy to be styled and click the appropriate style in the menu.