After reading Synchronize tag wikis across Stack Exchange sites I wondered: when editing a tag wiki, would it be possible to notify the user of other occurrences of the same tag on other Stack Exchange sites?
In other words, if I edit the tag wiki for mercurial on SO, I would be notified that a tag with the same name appears on SF and SU. The tone and focus of the tag wikis on each site would be different, but if updating factual information common to more than one site, it would prompt the user that there may be other locations that would benefit from the same update.
