Emphasized and italic text
Emphasized (or italic) text is marked by single or double underscores.
Textile example: Emphasized and italic text
_Emphasized_ or __italic__ text is displayed by browsers identically as italic text. Therefore, these tags can be used interchangingly most times.
Textile input (editable)
More about: Emphasized and italic text
1. For markup within a word, square brackets
[ ... ] have to be be used:
The words [_e_]ffect and [_a_]ffect do not have the same meaning.