Background
A new Checkbox has been added. This Checkbox is labeled "Delete Comment After Posting". Why would you check this Checkbox?
When a comment is posted an email is sent to the channel's email address. If you want the information you are posting to be viewed only by the owner of the channel or video (via email), you should check the box. If you do so, the comment is posted,YouTube sends an email to the channel's email address and then the comment is deleted. This prevents the comment from being viewed by others and marked as spam.
However, if you want the comment to be viewed by others within YouTube do not check the box.
NOTE: Share Video now looks for a recent video posted by a user and posts a comment on the video. We do this since YouTube eliminated sharing videos with YouTube channels. Therefore, this Checkbox exists for Share Video as well as the Post Comment features.