Earlier quoted context omitted.
Well, pain exists for a reason for animals to pay attention to things that are harming the body. If you remove the flag (pain), harm will continue.
That's a very real concern. A friend of mine has a higher than normal threshold for pain and have permanent injuries as a result. Among other things has walked around on a broken foot for months and failed to register a back injury. All of this then escalated to the point where she feels the pain, but the injuries have become permanent.
A rheumatologist explained to me that in people with chronic pain from things like arthritis, the brain's pain perception can become permanently altered to register pain that no longer "exists". She explained that the brain itself is really the source of the sensation of pain, and you don't necessarily need a "real" source producing a signal. So one should at least not ignore pain if one can avoid it.