You can use math to calculate the expected value of the user's balance.
You can use math to calculate the expected value of the user's balance, but it is still a possibility.
In terms of calculating how much a user lost, it should be fine to use mathematical ev. You can't say that the ev of the dice game shouldn't be calculated just because there's a possibility that players or the house can win all the coins.
These kinds of bonus should come with terms and conditions to avoid unethical actions from players (such as the mentioned loop). This is how the bonus algorithm should work, otherwise, if your funds remain the same while canceling the bonus, everyone will claim the bonus and cancel whenever they lose the bonus, they can simply claim again and continue the loop afterward.
I agree fully with these statements. That, however, is neither the argument nor the problem.
To make it clear, you are not being forced to bet, your funds will remain in the balance if you did not wager(lose) it, for example, if you make a deposit, you claim the bonus and immediately cancel the bonus, you won't lose anything, or maybe if you make a few bets which resulting in lose, this is the only way that affecting your balance, which means the player funds are being use for wager before the bonus funds, and this should be mentioned in the terms and conditions to avoid any misleading.
I don't think you understand exactly how it works. The player's funds are NOT being used for wagering. The player's balance is a sum of the bonus and their original deposit (+ whatever else they gained). How their bonus system works is that for every winning bet, the locked balance goes up and when one wants to cancel, the locked balance is a sum of the bonus amount + gross profit (not net profit).
Spreading negativity will not help the case. Although it was the player fault for not reading anything before proceeding to click the cancel button. Duckdice has refund the player's deposit. The player should read and ask before performing those action, but he didn't. In this case, I can only see that the terms and conditions are not clear, which could misleading part of the players.
Shouldn't be considered the fault of the player for something they are not in control of. If one deposits, claims the bonus for a total of 2 BTC for example (1 BTC deposit + 1 BTC bonus) and subsequently wagers that amount twice: winning and losing, then they are back to where they started. If they wanted to cancel because they didn't like the odds, they are out of that option because the locked balance is now equivalent to 3 BTC. Canceling would result in a balance of zero.