Not a Chat mod, but a Discussions mod - to keep an eye on things in Discussions.
The Clash of Clans Wiki app is very popular and Discussions is very active because of it, but by and large, the users there don't know the rest of the wiki too well, or its rules (we have seen several cases where users try to sell town halls for actual money). There already are Discussions moderators on this wiki, and I have no reason to think that they're not doing a very good job, but this is a task big enough for more than one or even two, so that someone can always be around to look out for bad posts.
On a few other communities, we've had really good experiences with Discussions mods who were app-users only, not even regular editors on the wiki. They are usually online a lot, and even though they're not your usual wiki editors, they are inherently familiar with the Discussions crowd, and so can be a big help to the admins and other mods there.
I'm not sure what you mean by how far the chat goes. Discussions isn't a chat, it works like a forum, so all posts are visible to anyone all the way back to the very first one, if they care to scroll back that far.
At the moment, tools that work for flagging bad content on wiki pages don't work on Discussions yet, but we're working on it. Hopefully, before long we'll be able to monitor Discussions for really bad content, too, for example so that the VSTF can step in when there is spam in Discussions just like they do for wiki articles. For this wiki, a flag for terms like "sell clan" would certainly make sense.
He has already started! For admins (but only them), there is an Insights module on Discussions, where they can see who has been moderating most actively in the past 30 or 90 days: Discussions Insights. Regular users can't see this, unfortunately, but it's a useful tool for admins to see if their team is still actively helping.