The text editor relies on an activeX plugin on IE. As well as making the text editor appear, it gives the browser lots of other features such as Windows Updates being able to install software on your PC, other sites being able to scan your PC for viruses etc.
Firefox is considered safer partly because sites can't have this type of control over your PC by default - some sites try to execute malicious code on your PC via activeX.
You can either try to activate/install this feature on Firefox or download a plugin for it which lets you right click on a link and choose "Open Link Target in IE" and use IE just for certain pages.
http://ieview.mozdev.org/