Underage problems
There seems to be a bit of a trend of leaving notes to your servers on your bill. I find it a bit odd, as you can literally talk to these people in person. They come to your table! Anyway, often the notes revolve around not leaving a tip. I’m all for encouraging good service, but servers rely on tips to bring their wages up to a decent level.

There aren’t many reasons why you shouldn’t leave any tip at all, and your server following the law definitely isn’t one of them. If you’re underage and your server refuses to sell you alcohol, then they’re doing the right thing. It definitely doesn’t warrant you short-changing them. What a jerk.