Also, if you do the quick reply which is always at the bottom of the thread you are reading, it will be simple font. No bells and whistles to your response.
If you hit the reply button which is on the top right of each post in the thread you are reading, you will be able to respond using advanced editor.
The advanced editor allows you to embed youtube, add emoticons, change font and colors, and just do all kinds of things.
You have several choices to use depending upon how unique you wish your responses to be.
