BU's fundamental purpose is Semi-Unrestricted block building (accelerates network centralization).
CORE's fundamental purpose is Semi-Restricted block building (preserves network decentralization).
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How decentralised is LN?
I am not qualified to answer.
In theory, if designed and implemented appropriately, equal to Bitcoin's.
It would seem the former of these two options was envisiged by the creator at the time. Nodes centralising around well connected mining nodes and bitcoin service providers, and users using SPV wallets.
Yes, but there is one problem that is a constant misunderstanding in the
whole Bitcoin community.
When this belief was stated by Satoshi, Nodes were a single entity.
The miners were validators and the validators were miners.
There was only one. Now, there are two separate systems.
Due to these two separate systems, there are two possible choices now.
Satoshi's original comments (as to Nodes) no longer apply to today's reality.