I totally get the rage about this during the performance and I have told people to put their phone away numerous times at the cinema and theatre.
I really don’t understand why you have no tolerance “especially during the interval” though. How could it be worse to do it in the interval?
For a start, some people often go to the cinema or theatre on their own, so are they just supposed to hope random strangers want to talk to them and otherwise just stare straight ahead and wait for it to start again?