Unlike with English letters, if you apply boldface to a complex Chinese/Japanese character, it might turn into an indecipherable blob. If you know the language, you might still be able to read it, but it is strenuous for the eyes and it does nto look good at all.

Bolding is much less used with Asian characters than with other scripts. Where boldface is required, it is usually replaced with a larger size character (for example, from normal size 11 to size 14), or by using a different/bold style font such as "Hei Ti" font.

Italics are almost never used with Asian scripts as it destroys the aesthetics of the characters and makes them harder to read. Again, it is usually replaced with a different style font such as "Kai Ti" font.