Unless you're an idiot?
Rosamund Pike calls out audience member for texting during show
https://www.bbc.co.uk/news/articles/c0723zgdp0eo
Given how many posters there are here, there must be those who think it's reasonable behaviour to text or film during performances.
We watched RP in this play (Inter Alia) and it's an incredibly intense experience. I just can't understand the mentality of someone who would pull out their phone and text during a performance.