The majority of people are slightly surprised. Most of the time they don't realize they interrupted or that it affected me. My entire family on my mother's side are either chronic interrupting types or shout out random bits of conversation you aren't part of types. My mother often answers back that of course what I'm talking about is trivial and unimportant so I politely thank her for being honest and walk away. Within a few minutes she realizes I'm not affected by her narcissism anymore and won't apologize for protecting myself. I also walk out when my family starts bickering without saying anything.
Basically, my family will argue and bicker in order to prove their point of view is right and everyone is miserable. I choose happy and refuse to engage in conversations or be in the same physical location as dysfunction. I'm 50 and life is too short to live it in misery or trying to prove something to someone who doesn't care about my point of view.
It's sill weird for me sometimes, but I would rather feel a bit awkward and feel happier than fit into dysfunction and feel miserable.