User blog comment:The Milkman/Extended Expectations, Part II/@comment-1441235-20120629062602/@comment-4953843-20120629213240

if harby detected a reaper IFF in front of him that should've raised some alarms - thinking to himself or hollering at his reaper bros, "oi! do we have a destroyer at coordinates --? which one of you lot's in my face yer blocking my lazers!" nobody bothered to respond, or responded too slowly, it seems.

it's more the implication of reapers underestimating their enemies rather than any real logic faults of the attempted catch-all explanation, really. see above posts again. they failed in countering sophisticated systems, so why not look for a simpler solution given the aggregate wisdom of the countless species they've assimilated? eyes/optical devices, ffs. anything that can scan for EM wavelengths 380 nanometers to 740 in technobabble. again, they didn't. so apparently it's an ego thing.

for the third time, i'm saying the normandy lucked out because of accumulated mistakes like that and the fortuitous inclusion of certain personnel and tech. i refuse to attribute the normandy's survival on the IFF alone.