My QA team are observers on all bug and support traffic. They aren’t required to respond to any of it or even to read it all, but they are expected to skim it. If nothing else this gives a flavour of where current issues are in the released and in-development builds.
But we find it’s more valuable than that. It generates test ideas based on customer scenarios, or even asides or expressions of interest in future features. It means that we can provide a more informed user viewpoint for product decisions, alongside our customer-facing colleagues. It’s also not uncommon for QA staff to provide information that helps the support staff identify issues.
With the overview we get, we can join the dots across the product. We reduce the number of dupes that are filed, we spread knowledge of fixes that may affect repro of other bugs, we often find that an issue that someone has seen sporadically and not filed because they can’t repro will be related to another ticket and we get a more complete report, more evidence and so on.