-What I understand from both replies that Bitcoin core doesn't allow transactions with total fee/cost less than dust value, but does NOT prevent u from creating dust UTXOS so they will be ( I mean still) stored burdening the system status (because the owner won't spend them) as the paper says.
You can't create and push a transaction that contains a dust output with Bitcoin Core. It's just that they're nonstandard and including it in a block almost always involves the participation of a miner.
(This is again about my research proposal of classifying UTXOS into types, I just find it hard to believe no one did it before & no one is even convinced to do it; here I mean dust like burned not likely to be spent in the near future, why not accumulate their hashes separately?)
Dust are sometimes in fact spent by the user to get rid of them from their wallet so they won't spend it inadvertently down the line. You need to keep them in an index in case they get spent for whatever reason. Most of the time, it's spent to an OP_return, whenever it doesn't cost more to spend it.
I don't think it is necessarily a bad idea to exclude them. I'd imagine the actual resource savings would be very low though. You might have to spend more time validating blocks if they ever get spent; you can't get them from the UTXO set directly.
- For the mark "Unspendable" maybe the Samourai wallet was doing that in purpose, I mean preventing them from being included in any valid block as they know they're part of a hack?
(I'm just concluding from the article, I don't know for sure)
You can't prevent UTXOs from being spent, unless you're the only person that can spend it. It is intentionally marked that way to prevent it from compromising the privacy of their user.