I'm not making excuses for anyone, but I've accidentally done this. On my phone and messaging app, if I read a text and leave the conversation open (not exiting the thread and the app) I won't get any further notifications from that person no matter how much they text. I'm sure it's a setting somewhere, but the setting is dumb. Like, surely I don't want a bunch of pings when I'm actively conversing with someone and looking at the app, but leaving the thread open and the screen off "should" still get a notification, even if the app is open under my lock screen.