When you right click on file/folder in detailed mode, it won't open menu for the file unless you click on the first column. I don't know if it is intention or bug. But if it new feature, you should at least let us select on which columns it should work as we are used to and on which in this new way. The same also applies on drag and drop.
This is intentional to fix various bugs with the details view (as far as possible). It's documented on the website. See bug #11605. It is the first column because that is usually the column showing the file name.
Usually but not always. I like my name column on the right, and i believe im not alone who isnt convention following zombie. Why dont you let us choose the columns we want to behave this way?
Fixed in http://git.xfce.org/xfce/thunar/commit/?id=1ba30278f554c3003170b46405031ef27f2d443a