Such a forum could be very useful.
It is important for divers to be aware of how gear can fail. How to prevent it. How to overcome a failure. In my OW class I was told that modern regulators are designed to fail open, freeflow. Later I found out that they do not always work as they are designed to, and can fail shut - no air.
Customer feedback. For obvious reasons manufacturers would not be thrilled about such a forum where their defective products are exposed. But it could be useful in providing actual use product feedback. Allowing them to guage extent and promptly fix the fault if necessary. Many people with minor product issues, such as small bc bladder leak, choose to repair the bladder instead of returning it.
Divers can learn of defective and inferior quality products to avoid. A safety issue from the divers perspective.
It can help steer manufacturers towards greater diligence before product release, and quicker response in addressing product issues.
And even the small stuff can be important underwater. Regs shouldn't freeflow. Is it a product defect causing an inordinate number of freeflows in a particular reg, or other? Wings, hoses, connections shouldn't leak at all. Straps shouldn't brake. Connections shouldn't easily disconnect, inadvertently.