Can someone tell if this really work on some case, decrease payment instead of preserve. AFAIK bump fee usually work as it says, same amount but much larger fee. As the electrum recommends, it probably only work on increasing fees.
I did it before and it worked.
Technically, there is no reason why it won’t.
Bump fee is nothing but canceling the unconfirmed transaction by replacing it with a new one. You only need to pay higher fees and make sure the replacement transaction spend
at least one of the intial transaction inputs.
Preserve payment means you will send the same amount and use other UTXO(s) to cover the extra fees. While decrease payment means you will deduct the extra fees from the amount to be sent. This option comes in hand when sending the max amount and you don’t have any coins left to cover the extra fees.