Page comments are useful for capturing improvements and issues; however, the comments persist past page major revisions. In theory, I see the following:
Someone comments on a page
Author responds
Page is updated; comment is addressed
At this point, the comment should be deleted since it has been addressed in the page contents and no longer applies. It seems like a hassle to have everyone delete their own comments after page revision.
Also, once deleted, comments are not visible when viewing a previous revision of a page. The total number of comments is listed, but no comments are visible. We need to be able to review old (deleted) comments so that we see the chain of events page v1->comment->page v2… etc.
Interesting use case. However not all comments are related to things that need to be fixed in the page and there’s no way we can guess that
So deleting a comment that doesn’t make sense anymore seems the simplest approach.
Note that if you use annotations (which are special type of comments), then we already have the notion of stale annotations when the content on which they are has been changed/removed. In this case we don’t display them. I don’t think we remove the xobjects for that when that happens but that could be a possibility/feature (that could be configured in http://extensions.xwiki.org/xwiki/bin/view/Extension/Annotations%20Application#HConfigureannotations ).
