To those who yell like, "She'll peck your eyes out!", "She'll tear your face!".
She won't. But NEVER try to do this with any random owl you meet, because those might do exactly that. I've been raising Yoll since her 2 weeks old; I know her habits, I can determine her mood and intentions, and I understand what she would or would not want to do at any given moment of time. That's exactly why I know when I can shove my face at her like that and get away with it.
It's called grooming. Owls who are friendly to each other often do mutual preening and combing. Thus, beak poking (and accepting it) is essentially a display of favor and friendliness. If an owl doesn't feel like being friendly, it'll leave. If you keep insisting, it'll bite you in attempt to make you leave it alone.
I wouldn't shove myself like that at another eagle owl that I don't know. Or maybe I would, but not before spending a good chunk of time getting to know its personality and its opinion about me.