Really, I see absolutely no problem whatsoever with congratulating people for their accomplishments. Regardless of how "watered down" the ladders are, which is a bit true, arrogant as it is to say, it's still an impressive achievement to be #1 on a ladder. If any of you really think there is something ethically wrong with congratulating someone for their achievement, I really don't know what to say.
What do people work so hard to do for their birthdays? Not much at all. As long as the person isn't using the congratulations as a reason to be super arrogant, there is no folly with kind words.