What are the issues of running lightning daemon with pruning node? Most lightning implementations I came across don't officially support pruned full node. 


Why is pruned mode implementation a challenge?
What risk am I taking when I run lnd with pruned bitcoind?
Pruned nodes don't have the ability to make a full index of all transactions in the chain, which makes implementation of tools like Lightning difficult or impossible. There's no risk particularly, a pruned node has the same security properties as a normal one, it just doesn't have historical transaction data necessarily.