Quote from: stompix on Today at 02:19:55 PM

So, what happens if I send a transaction of 1BTC with a fee of 0.99 BTC?
I will be a bad creditor but at the same time, all the money is lost, so who will cover for this loss?

If you (as a bad issuer) decide to waste your money, absolutely you can do it and you can harm The related creditors maximum 20,000 Satoshi in each transaction as well. In this case no one will cover creditors lost. But how many of these crazy guys exist?
Instead if you ask me "What if issuer is miner as well", I can address this on paper the answer of "What if issuer is miner as well?"

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you have only counted a simple tx, not if he plans to combine inputs and use it to pay to different outputs,...
There are only two type of transactions, first type is what Sabu clients(mobile wallets) consider as a valid transaction and second type is all combination of inputs and outputs and...

No one can force the issuers(UTXOs owner) to use and spent the UTXOs in a certain way. Issuer can deliver to a creditor a valid transaction, and later try to spend it in a counter-promising manner,
But because of limitations that wallet already forced to transaction format and amounts cheating chance is in minimum. Take a look at https://github.com/raymaot/transaction-numbers-and-coefficients and also other transaction control.

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And now to the SABU protocol, it's a centralized system, right?

The Sabu protocol is the most decentralized system ever. Please study "The network architecture" in article.