The instructions on reporting a bug are absurd–designed to prevent bug reports. There is no way to access the overly burdensome template while creating a message, so what good is the template.
On to the bug:
It is impossible to turn off reader mode. When a page allows reader mode (which Brave cleverly calls speedreader even though that is an inaccurate name).
I have seen that this has already been reported and is acknowledged as a bug: