That is not right at all
So I am on the level 10 in Dutch
so to make the long story short it is displayed here:
but not here:
I think it's a glitch with some users that Duolingo is currently trying to fix (and has, already, partially fixed now). Right now, I can see your Dutch badge and I can see mine, but I guess the "phantom badge" happens to some users in some of the discussions (sometimes I still can't see my Dutch badge in a comment I make).
EDIT: I looked at your comment again and it's disappeared (but I can still see mine).
For me the Dutch flag doesn't show for either of you. Indeed it seems to come and go. I think many have reported this, and I'm not sure if they already have done something to try and fix it, since it seems it has been like this from the start.