Accidentally, I discover hidden ability of TextEdit : Completing Word and Recognizing Font Style. Let's go through these two.
Completing Unfinished Word
Actually, this feature have already discussed in later article. However, I find a quicker way of doing these word completion.
For example, procrastinate will be a long word. Luckily, if we type it inside TextEdit, we just need to type procra and then press , list of TextEdit's words recommendation will be shown.

Use ↑ or ↓ to move the highlight, → to accept the highlighted word recomendation and ← to close list.
Font Style Hidden Preview
Have you ever curious how to see the font-style in TextEdit?
Open up your font-pane (with ) and move your cursor above the text that you want to be recognized, TextEdit will highlight the font-style in three separate columns.
T

In example above, the font-style is Bitstream Vera Serif Bold 11.0 pt.
But it's easier way I got here. Put your mouse cursor on the tiny hole located at the top-center of font-pane and then drag it down. New display will appear. Now, try to move cursor again to the same word as before. Let's see what you got.

Is it the same as before?