There are many things that Y can do.  Y can start a discussion on the talk page and ask X to participate.  Y can go to an appropriate noticeboard or WikiProject and ask for input from other editors.  Y can request that the page be protected.  But Y can't do any more reverts.  And it is not true that any edit that changes the text is a revert.  If you fix a spelling error, or clarify the wording, or substitute a better source, those are not reverts, unless you are returning the article to a state it was in earlier.  The basic problem is that you are seeing this as a fight, and trying to find a place to win.  If you are dealing with another editor who wants to fight, getting into a fight won't lead anywhere  what you need to do is get help.     