We usually post something to that effect, but not always. For one thing, not all the moderators are public. For another, posting that we made a punctuation change, or some such, is tedious.
But the important point is that on HN, titles do not belong to the submitter—they're shared—so submitters don't have any special rights over them. On the contrary, the site guidelines specifically ask them not to change an article's title unless it is misleading or linkbait: https://news.ycombinator.com/newsguidelines.html. Comments are very different, and we don't edit them without saying so, unless a user asks us to. (Though a few times I've broken down and corrected an obvious typo.)
But the important point is that on HN, titles do not belong to the submitter—they're shared—so submitters don't have any special rights over them. On the contrary, the site guidelines specifically ask them not to change an article's title unless it is misleading or linkbait: https://news.ycombinator.com/newsguidelines.html. Comments are very different, and we don't edit them without saying so, unless a user asks us to. (Though a few times I've broken down and corrected an obvious typo.)