[Gonso]

I deal BJ occasionally (in the US), and yes, the dealer should have let the guy wave off his 17 before moving on to the next player. Obv those with BJ/21 don't get an option, and I pretty much go through the motions with 20's and typically 19's with 99% of players.

With hands like a hard 17 or 18 against a dealer 6 (which is a no-brainer stand for those who don't play BJ), you most definitely have to get a hand signal. There are way too many people who want to pull angles like your friend probably did. Either than or he has no idea what he's doing.

Now, he could have had a soft 17 with A6 (you didn't specify), and in that case the standard play is to double down against a dealer 6.

In cases where a player does something like this, we don't back the cards up where I work. What will typically happen is that they'll take care of the player somehow, and the dealer will be instructed to get clear hand signals for everything from that player - and I mean everything, no matter how obvious. The guy has AA and wants to split? Make sure he gives the split sign. He has 20? Get a hand signal. Wants to double down on 55? Get the one-card signal so he doesn't come back and say he wanted a split. Then they'll put it in the computer to alert other supervisors on that guest's future visits.