New thing time! You can now edit your own comments.
Hover over your own comment to reveal the pencil icon in the upper right:
Click it to edit the comment:
Make your changes (Markdown!) then click Update Comment to save it or Cancel to bail.
Fairly obvious benefits =). We think it will be particularly useful for those just learning Markdown, as you can give it a shot and fix up mistakes rather than be scared of it and not use it.