~labrat Thank you for the patch. So far, it is working great! Will message when I stumble upon a bug.
I have the same problem with the maildir backend ~yaymukund's patch also fixed the notification problem for me. Would be nice to see this on master, even without the disk persistence.
Currently if a user switches between the ticket overview and a singular ticket the "Enable notification" button stays at the same position and looks almost the same (except it is now called "enable notification"). It might not be clear for a user that it has now a different function (subscribing to the notifications of a single ticket instead of the whole tracker).