Did you ever read the Hitchhiker's Guide to the Galaxy trilogy? In it, Douglas Adams writes of a planet whose entire population has evolved into birds, their once-thriving economy decimated by passing the so-called Shoe Event Horizon, in which people buying shoes causes people to open more shoe shops and to produce more shoes of lesser quality, which causes people to buy even more shoes, which opens even more shoe shops, until the entire economy becomes based on shoe shops and everything breaks down.

I fear a similar problem occurring on the Internet, except with graphical smilies. So my vote is "no." After all, this is a tool for getting things done, not for looking at faces sticking their tongues out.

http://en.wikipedia.org/wiki/Shoe_Event_Horizon

I agree with ryandesign. This is not a bb-type application.

But... It can be usefull to add some styling to a page. And those strange signs can be iritating... And its quite simple to add...

Can u make it as an option?

You have the option to make your own adaptions of the code.
Please don't ruin this nice tool with irrelevancies.

This can be a good candidate to be implemented using the Mantis Plug-in Display filters once they are implemented. See related wiki page for more details:

http://wiki.mantisbugtracker.com/doku.php/mantisbt:addson_requirements

These plug-ins are not yet supported, but at least the vision is there!

Such functionality can now be addressed via plugins like the one below which adds Markdown support:
https://github.com/mantisbt-plugins/Markdown