Who ensures that LN does not become bitcoins DAO like experience?
That's not really relevant here. Let's all stop any advanced development because an incompetent team failed with their pump & dump coin? I think not. Peer reviews and extensive testing 'ensure' that. Although one can never be 100% sure.
It's a totally relevant! Rather than test LN and its base code SegWit, (bitcoin's DAO), in the real world befor deploying it on a $10B network, why shouldn't SegWit be deployed and tested in the real world on an altcoin before being implemented in Bitcoin?
It's being tested on the Elements Alpha sidechain for over 12 months, segnet for 6 months and now on testnet3 for the last 7 weeks ... so what kind of altcoin did you have in mind specifically that would be needed in addition to these?