I know you should not speak to someone from within a bathroom to someone outside. However, is it permissible to speak to another person in a bathroom? For example, in a public bathroom where there are urinal stalls – would it be permissible to talk to someone else?
One should not speak in the bathroom unless there is a great necessity to do so.
Brachos 62a, Rambam Deos 5:6, O:CH 3:1 & Mishnah Berurah 4