S&W has had some questionable "features" on their guns. Magazine disconnect on the old 3rd-gen semi-autos, internal locks on revolvers, manual safeties on striker-fired pistols, although at least you can buy an M&P without the safety. The magazine disconnect had a purpose for LE in cases where a perp grabs an officer's gun, although it's debatable whether the LEO would even be able to drop the mag every time. The manual safety can help prevent Glock Leg, but requires specific training. The internal lock on a revolver is most worthless, IMHO, as it offers no safety while carrying as it must be unlocked, and for safe storage an external lock works just as well plus offers visual evidence of condition. And there's a very small chance the internal lock can fail and cause the gun to be inoperable when it's needed most, and that cannot be remedied in the field. Fortunately these failures appear to be extremely rare, and I have never met anyone who has had it happen to them. If it was a big problem it surely would have eaten significantly into S&W sales.