Congratulations on your success!
Recently, there was a thread where several people said they
never comment on someone's weight loss because they feel it is inappropriate to
ever say anything unsolicited about another person's body. Also, many people here have said that they do not like people to mention their weight loss, or especially say, "You look great!" because it implies they looked bad before. So people may very well be noticing your loss -- in fact, you've lost so much, they must be! -- but feel the polite thing is to not mention this.
I have a friend here who is quite overweight and has been losing. She's mentioned to me a few times that's she's eating low-carb and walking more. I'm so happy for her, but I'm unsure what to say, now that I know some people are uncomfortable with comments. One time I said, "You've lost a lot of weight haven't you?" and she kind of brushed it aside with a well, yeah, some (I think because she still has a lot to go) and I just said, "Well, you've been working hard, and it shows." I'm hoping that was OK