Depends on the environment, the person, and the situation.
You're talking about looking at someone's eyes in their reflection on the window's glass, right? If someone is doing that to me, well, where am I? Is it at work? Maybe they are just looking in that direction while thinking about something else, and not looking into my eyes purposefully. Or maybe they are just looking at me in general & not my eyes, depends on how sharp & clear the image is, or the distance, etc. Maybe they just think that you're of special needs, or perhaps that you are being rude.