[xwiki-devs] Some kind of DocumentChangedListener?

Hello, Is there any way to add some code without recompiling xwiki-core (plugin? component?) that could register a listener for any changes in documents (preferably by mask / type, as in "listen for added comments on Main.* and Blog.*") and optionally veto (and/or flag for review?) them? If not, please consider adding it - it would be a very nice way to make writing things like spam- and vandal- filters easier. It would also allow making such things more modular - if any plugin could register such a listener, then there could be (for example) two independent plugins running at once, one handling scenarios like "bad source" - "bad ip", "possible anonymous proxy", the other "bad content" - "bad words", "structure looks like spam" or "too many links". Greetings, Lilianne