Italicization is marked with two characters: < (start) and > (end). In edit mode these characters are shown in the edit window. In display mode the actual result of the italicization is shown if the font chosen allows it.
If only one italicization marker is put either in front of a line ...
<like this
... or after a line ...
like this>
... the program will automatically put the missing marker when the subtitle is updated:
<like this>
Alt+I
See also: