This sounds almost cynical, but this is what a nose that gets you disqualified looks like.
This pair got disqualified on the basis of an excessively tight noseband. There were no stewards checking tack at this show (or, at least not for the dressage horses), so it was up to the judges to notice any illegal tack.
It's obvious that show organizers are trying to pay more attention to welfare issues, but since there are still very few general rules for shows at local level in this regard, they all seem to do their own thing. Some shows now have stewards armed with cameras supervising the warm-up arenas, some shows do actually check your tack, and some shows give a fair-riding or welfare award to riders.
And then there's the old ladies by the ringside who'll angrily mumble things like "that child needs a lunge line lesson, not an FEI pony" which I still consider the most effective method of quality control. But then again that might just be me being terrified of old women's opinions.