Ask HN: No longer allowed to comment on your own submission?

My previous understanding was that, after submitting a URL, it was polite to post a comment saying basically what you thought was interesting / worth reading about the article.

It looks like HN has changed this so that you cannot comment on an article after you submit it.

Sorry if this was already announced, I did try to search for an announcement and didn’t see one. If it wasn’t announced, I’m just curious what the motivation was for this change. Does anyone know?