BitcoinCasino.io is kindly inviting you to resolve this issue here or via private message.
We will do our best to keep you satisfied!
What you mean kindly inviting? He's already put his accusation on the table and you're supposed to tell us if he really had multiple accounts or something else? Discussing it here in this thread is much better to keep your operations transparent and hence gain somewhat reliability for your website.
Still he didn't provided his username yet for BitcoinCasino to check through his case. Though I agree that the discussion should be public.
You should post more info, screenshot transactions etc.
Keep in mind is hard for a casino to put their reputation at risk for 20$, everything can be but is a low amount.
And that amount too coming out from promotions likely. I think he most likely played the free spin promotions and you know how free spin promotions are abused.