A couple of things:
1 - When you're clearing out your journal make sure you clear out *everything*. The first time I did it I didn't realize there were sections for 'Collections' and 'Completed Quests'.
2 - Completing that horse racing quest in the Hinterlands seems to have had some effect. I completely ignored it at first because I didn't really want to have anything to do with the mounts but then I saw some one on reddit say they had done the same thing, went back to complete it, and started getting banters again. So far I've had a few banters after completing it, not as many as I think should be normal but more than I've been getting for a while.
And for my completely uneducated guess as to what's wrong: there's a RNG or script that's meant to fire off at certain intervals with a set chance to succeed. If it succeeds, we get a banter, if not, well no banter. For most people the chance to succeed is high, for us with the bug it gets borked and the chances are extremely low. Most of these 'solutions' happen to reset that script or RNG, temporarily giving us banters at regular intervals. For a lucky few it stays fixed, for the rest of us it eventually breaks again.