How to hide the Comment section on a Transition Popup

Create a field of the "Message Custom Field (for edit)" Type (from JIRA Toolkit) - name it someting like: "Hide Comment Field":

Set the Default Configuration to:

<style>
#comment-wiki-edit {display:none; visibility:hidden;}
.comment-input {display:none; visibility:hidden;}
</style>

Add it on the Screen, and the Comment field is hidden.