you choosing to settle and pay up the debt or the other party decides to call in the debt. are both are still part of 'buy now pay later' known schemes
bitcoin is not deposited into LN.. bitcoin never leaves the bitcoin network
as for the LN balance that goes back and forth and renegotiated.. they certainly can double spend the UTXO reference across multiple channels. there is no network wide audit in LN(as for who eventually gets to win that actual amount at settling.. only one will and it may not be your rented channel/temp channel)
and secondly assuming the honour of only using one UTXO reference as collateral for one channel.. that becomes.. wait for it "credit limit" thus even in honourable facilitation of liquidity.. the reference is just a reference of credit limit
as for extracting value. there are many ways to cheat the punishments and evade the processes.. this is why LN didnt function via just punishments but now needs things like "watch towers" and other third parties to act as escrow and other means t prevent cheating
heck there are services that do the opposite of honourable credit
look at all the services that have channels that are years old but use that reference to rent temporary channels of inbound balance
the renter is not forming some funding lock to have 50% signing control of the value as that value was locked years ago
they are just shown some meaningless amount/balance from a reference they are not part of. and that can be taken away from them easily as they are not part of the signing process.. the actual UTXO owner can just sign his own tx on his own and broadcast it with a higher fee than the "state" the renter was supposedly given
..
here is the thing
try to put all the fluffy dream utopian promotional words you ever heard about LN into a box. and tape the box up and put it aside
then do this
imagine someone has invited you to put your hard earned value into a system.. and instead of blindly reading fluffy utopia. you decide you want to scrutinise it. and test it for bugs, and battle test it for weaknesses..
now just try to not think of LN as the happy dream they promoted to you. and instead think of it as a financial system that should be scrutinised before risking value in..
have fun finding the flaws instead of finding ways to ignore the flaws.. remember its your value risk you are putting up when you play ignorant or avoid wanting to see things outside of the PR game
dont fear scrutinising something when its your money on the line.. the devs wont refund you