One of the plans which I had told my contacts about, was that if they send me SMS messages – i.e. phone-texts – the understanding would be that my phone would shout at me, to implore me to answer at once – therefore, for them to use SMS in an emergency.
OTOH, It can happen that one of my friends might like to chat with me, but without causing me to become a distraction to people around me. My phone should notify me noticeably-to-me, but silently. For that purpose, I still recommend that people use Facebook Messenger.
For some time, it was working that way for me, but at some later time, this had stopped working, in that each time I received a FB Messenger Chat Head, my phone had started to give me an audible notification again, which I had some trouble suppressing, in spite of the improvements that Android 7 brought to my Phone!
However, since recent months, I’ve gotten FB Messenger notifications to behave again, exactly as I want them to. And here is how I fixed the problem: