Oh that, lol.
I knew about it a long time ago. But I never bothered to record it, because I'm not getting bandicam just like I'm not getting a ts.
So with /feed, even if you have full hunger, sooner or later you'll lose half a bar. Like never losing hunger after that, you will never gain hunger points after eating. It's annoying, yes.
There's "/feed off" too btw, so if you lose the half hunger and want to farm, use that, eat something, then turn on /feed again and farm. You should not be able to eat anything until the 1/2 hunger is lost again.