At first, I was able to get banter by using the horse in camp trick. That stopped working. Then I moved to fast travel from war table. That was good but stopped working. Then I tried the updating journal and codex. It also appears to no longer be working. All of these workarounds are a lot of work and detract from the experience.
My first playthrough was 144 hrs. I did not discover the banter bug existed until 130hr mark. I just assumed two things - Bioware did not have as much banter this game and they did not launch with the option for us to respond during banter. Imagine my shock when I found out that it was a defect. I had very little banter first playthrough (about 20. know this because I have been trying record all party conversations). Also, in my first playthrough, I only had one conversation where I could respond. In my second one, I have had two so far - one after solidifying my romance and one not related to the relationship.
Second playthrough now at 90hr mark. Many of the fixes I did above helped. However, I still have gone long span of time with no banter. And this is in places where I know there should be some. I think being online is part of the cause. I forgot to go offline last night and had no banter in almost 3 hrs. Then today went offline, and bam banter every 3-5 mins.
In my two playthroughs, I can attest to the following - Western Approach is broken. In over 200 hrs, I have only had 2 banter convos in that area and those might have been triggered events.
Also, even with the workarounds, the banter bug can return. It may have something to do with quest updating or even the number of save files (deleted a ton of save files on 2nd playthrough and banter started up again). Not sure but the bug seems to happen unless you play a specific way - only fast traveling from war table, constantly ticking off your journal and codex. Since most people will not play this way normally, it explains why so many of us have this bug. It diminishes an otherwise great experience.