I use mbasic.facebook.com on my phone (since there is no messenger on facebook's mobile site). Reading messages on mbasic doesn't remove the "new messages" noti

I use mbasic.facebook.com on my phone (since there is no messenger on facebook's mobile site). Reading messages on mbasic doesn't remove the "new messages" notification from the regular website. That is to say, this might also be a technical issue, i.e they keep state of "messages read" per front-end. And, of course, it's an engagement thing probably, too.