Larry: commit messages are for other developers, which news entries are ultimately for users.  Some developers want (insist on) the freedom to make the two different, with different details.  I am using that for Idle patches since NEWS entries become 'What New for Idle' in each release.

Brett, I presume that you mean a new NEWS box like this Comment box, maybe with 3 lines and a new Section: box like Components.  Question: Is it impossible to put labels above a box rather than to the right?   

We could allow that news section to be (initially) filled out by someone other than the committer.  Latter could (optionally) copy and paste as (initial draft of) commit message.  Having message visible on issue might result in typos being corrected sooner, and would make it much easier to edit news message later (But editing after close should be limited to core devs).

Larry, a commit hook would be better that a separate pyci since TortoiseHG [Commit] button would still work.  With Brett's solution, a commit hook could email commit message to tracker as NEWS message (if empty).  And yes, change should apply to all versions.  Otherwise, NEWS commits to older versions would have to be null-merged.