@Anonymous
interesting question,
I want the script to be independent from me and my own server. If a scanlation team want to distribute their own information about their overlays, without using my own server as intermediary, I want it to be possible.
Consequently, by design, at the very minimum some data has to be stored on localStorage (which is the poor man way of being able to configure an userscript/bookmarklet): the server adresses.
This would allow users to remove my own server if they so desire, and/or add others instead (to this day, none exists though, I've originally setup BlackHorus' feed as a way to understand by example multi-feed requirements, but it's my own server aswell).
By "server", I mean places where information about overlays (where to find them) is available.
To adress the problem you've mentionned, I should simply add the listing of the servers stored in localStorage, and offer a button which "refreshes" them (ping them as if it was the first time).
Basic information about the webtoons is stored aswell, to avoid constant traffic between all the servers (faster, less spying on user activity, etc...), but it isn't yet very well implemented as we are very far from managing a big list of webtoons. I don't recall if I edited the "modified_at" date for fluttering feelings, but in the case I have, the problem you mentionned should resolve itself within a week anyway: past some inactivity limit, a server will be automatically refreshed (to check if there's new projects, things like that).