Maybe you can check this yourself now: a power user like someone who is already a mod got some additional menu items in "More…" under each post, which includes “Appoint as moderator”. So basically, they can appoint a random poster as a mod if they want to.
A similar thing has happened to me and I too was wondered when, why and from where this status came 😕
but practically it’s mostly like just an honorary title. So far the only time when being a mod ever actually mattered was, when someone cross-posted an ad massively and several users sent reports, saying it was spam and should be removed. Such a problem is very rare in a small community so maybe you don’t need to worry about it… It simply means, someone somehow judged, reasonably or otherwise, that you were a trustworthy user.
Technically, if you’d like to, you can use your new power to appoint another mod so you may not be alone :)
