For @stranger_in_a_strange_land and others who might like to know: after you post a comment, you have about ten minutes to edit it or add to it. As long as ‘Edit this response’ shows in red below and to the right of your post, you can make changes. I have a lot of afterthoughts (and I like to fix my typos), so I use this feature all the time.
When we make major changes, especially after someone has responded to us or GA’d us, we usually indicate ”[Edit]” so others will know it was changed after posting.