You can add typographic elements in addition to the element to which a character format is mapped.
To include typographic elements in DITA XML output:
[Typographics] ; UseTypographicElements = No (XML default, suppress b, i, u, tt, sub, ; and sup even when specified in a format) or Yes (HTML default) UseTypographicElements = Yes
When UseTypographicElements=Yes, typographic elements b, i, u, tt, sup, and sub appear in DITA XML output in addition to any elements to which character formats are mapped.
If any character formats are mapped to elements, and your project configuration file includes a UseTypographicElements setting, to avoid double nesting make sure you use the XML default value: UseTypographicElements=No.
Incorporate typographic elements sparingly, especially if you are using <outputclass>; see §24.4.6.6 Providing outputclass attributes for all elements. DITA asks for semantic, not presentational, tags. It is best to let CSS handle the presentation later.