Comment 1 for bug 1404234

I know of no (resonable) way to support icons on comment type columns.
The support for it in the previous releases was broken, in that it would work
if there was no actual content being rendered in the cell, but, if there was,
the content would be rendered on top of the icon, instead of beside it,
as with all other columns.

If you want to display an "is set" type icon, display it in another
column, using a template, which you can place right next to the comments
type column, to give you almost the same thing.

 status wontfix