I threw this up on the main meta but figure it's relevant here too. The description for Hat Trick is:
hit the reputation cap on three different days
I just earned this hat, but this is my reputation today so far. Note that I have two accepted answers, so I didn't actually hit the rep cap. I hope to actually earn the cap, but I haven't quite gotten there yet:
So either there's a bug in the hat calculations that don't actually take into account rep cap correctly or there's a bug in in the description for Hat Trick and it should just say "hit at least 200 reputation on three different days." Most likely, just fix the latter?