Since I installed the firefox extension greasemonkey I have been having additional text being inserted into htmlarea. The unformcant thing is that I like greasemonkey and didn't want to remove it. So I created a small extension which removed the chrome extension from the testarea when it is posted or the mode is changed to text.

To install just unpack the tar file into you plugins and then load it as you would with any other plugin.

Update: Clean Chrome has now been included into Xinha, and is no longer needed.