And here I am, just picking a local instance to support my fellow Canadians.

It definitely has its merits on certain types of discussion, but generally I sort comments by Top. I do sort my subscribed communities by New though, just to keep the topics fresh.

The instance admin has ultimate domain over all communities on their instance, regardless of where the mods hail from.

As I understand it, the community would simply carry on without a mod, until such a time that the site admin appointed a new mod. The content would remain, and other users would still be able to post to it etc.