The YUI Rich Text editor provides a more extensive set of button-ready options for formatting entry posts and pages. And, it can be customized for your exact needs.
You can see a video of the plugin in action below.
But what if you want to extend that rich text capability to your commenters? We can do that, too. There isn't a plugin available yet; but with a few simple template tweaks, you can have the YUI Rich Text editor installed on your comment message fields.
You can view a live example of this on the CNati message boards. A quick word of warning: You're giving your users a lot of rope with this add-on. You have to know your audience and trust them if you want to give them this much freedom! A screenshot is below to show the formatting options for commenters.
If you'd like to learn more about rich text options for Movable Type, including other plugins available for TinyMCE or FCKEditor or having custom buttons (like those CNati emoticons) let's talk.