[code]

there is way to widen post area. All you need is reduce post profile area so technically it will widen posting area. try pasting this code on your custom css

Admin panel => Display => color => Custom CSS Stylesheet


paste it on empty box (if there is any previous custom css)

Code:
.postprofile {
color: #536482;
margin: 5px 0 0px 0;
min-height: 80px;
border-left-style: solid;
border-left-width: 1px;
border-color: #ffffff;
width: 22%;
float: right;