You talk about SL chain, If SL meant "Second Layer" I'm letting you know that 2nd layer like lightning network are not chains.
Why are the blocks never full on BCH? Because nobody uses it or because the miners don't mind the ultra large server and extra centralization? If it cost 0.5 BCH to overload the BCH chain with sub 1 sat per byte transactions you'd have the same problem as on the BTC chain with just larger amount. People involved in a bidding war don't care about the fee paid on the rest of the block it only care about the fee of the double spend attempt transaction. There isn't even a way to have a bidding war on BCH, you get fucked or you don't (apparently because the miners on this chain are not profit driven).
The rule of the game have always been the same, First seen first included had always relied on the good behavior of the miners over profit. When you receive an RBF transaction the wallets notify you and tell you not to trust it a zero-conf .
I have no need to go to a reddit to learn about bitcoin, why do you bring this up?
RE: What I think makes Bitcoin Bitcoin, and why I think Bitcoin Cash is Bitcoin