Thank you for the information. Although I don't see a specific question, I am assuming you are asking if it would be advisable not to divulge your prior medical history when applying for the USMC. First, keep in mind that, as an officer of the court, I cannot advise you to violate the law. As you no doubt know, making a false statement on your application is a violation of Federal law. I am not sure who would be advising you to falsify your application, but hopefully not an attorney.
In any event, it is not generally the norm for DoDMERB and MEPS to share information unless they know that the other organization has made a determination in the case of a particular individual. In other words, they don't share the same computer system of records. So, it is quite possible that someone who is going through MEPS and is not honest about their prior enlistment or commissioning attempts and medical history can get through a MEPS evaluation and successfully join the military service.
That said, that would not be a guarantee that the medical information, either through DoDMERB or another source would never be discovered. If the Marine were to either later be injured or have medical problems, or perhaps have a security clearance investigation, and it was discovered that they had this previous medical issue that they didn't divulge and that they made a false statement on their application, then they would, at the very least face discharge from the service. They could also, face discipline, including court-martial for the false official statement and fraudulent enlistment. If, early in their service, the latter is not likely, but would be more likely if discovered later in their career.
All something to keep in mind when going forward. But again, there is no automatic sharing of this information between these two organizations. Please feel free to ask for clarification if needed. Thank you