This is the stupidest nitpick I've ever heard. Really? I wore a black shirt today. My girlfriend said I looked good in black. Guess what? I wore a black shirt a couple of days ago too.
Does that mean my girlfriend FORGOT that I have worn black before? NO!! She was giving me a compliment.
O'Brien saying that to Worf has nothing to do with either of them forgetting that Work used to be on the command track, it means O'Brien was giving Worf a compliment and congratulating him on his new position.
Seriously, are people's lives so empty that they actually complain about stuff like this?