I thought it used to be the case that if, in a Mathematica notebook Text cell, you typed the word Mathematica, the word was automatically was italicized.

This is not the situation with version 10.4.1.

Do I misremember?

In any case, I am aware than one can enable such automatic italicization for user-specified words AutoItalicWords and specify in either of two ways:

• in the Option Inspector, either globally or for the selected notebook, by setting the option AutoItalicWords; or

• in the notebook's stylesheet, editing the 'Local definition for style "Text"' Text cell as an expression, adding an AutoItalicWords option so that it becomes, e.g.:

  Cell[StyleData["Text"], AutoItalicWords->{"Mathematica", "Tensorial"}, FontSize->14]