Thanks all of you for your open and frank comments. I'm glad to see that pretty much all of you see things the way that I do.
Just to put matters straight (some of the later posters seem to think that it was I that took the comment as constituting sexual harassment), I was actually the passenger in question.
I made the comment to one of the FAs while I was deplaning. She said "thank you" very graciously (but also blushed quite obviously). A (female) colleague who was some way behind me and who had not heard what I said, but had seen the FA blush asked me what I had done to make her blush. I told her (and sincerely wish I hadn't!). She really took me to task for embarassing the "poor girl", putting her in a difficult situation and pretty much accused me of sexual harassment.
Well, after I had picked myself up off the floor, I started thinking about what she had said and figured that although my comment had certainly been a well-intentioned compliment, just maybe it had been perceived differently. I figured, who better to ask than FAs who deal with passengers regularly, which is why I turned to the Cabin Crew section of Pprune.
I am really much encouraged to read that most of you would perceive it as a compliment, just as it was intended. I hope the young lady in question did also.
Thanks again to all who bothered replying
Snoopy