Splicing is when you close and open channel at the same time so you can effectively enlarge or shrink channel.
This way Phoenix maintains only one channel with the user so there will be no dead channels that will be susceptible to force closing, and even if they need to force close a channel, the cost will be much lower as it'll just be one channel.

Tidy, clean, and efficient.
 

 Nice 👍👍 

 I see the potentials for LSPs like phoenix to be decentralised groups of nodes selling LSPs services non custodiallly 
Another improvement for LSPs would be users being able to run or subscribe to a watchtower service, so the LSP cannot steal (potentially) a users bunds (with an old state signed tx)