Ah yes, I noticed that, too. But I think, that is what Steve informed the team about yesterday here: Slow updates for comments and points?
Maybe we should use that thread for the new issue as follow-up thread, since it seems to be slightly different trouble now and Steve already started one.
@Samuli: Looks like it takes roughly two hours for the Communication stream to update, because I was led by your comment here and it showed up around 9 pm in my stream.
Could it be user-related? Your update took some hours to show up in Communications, but Matt's show up right away. 