I might just add : "on protocol level".

One can burn coins without any begative effect. Simply mine them or buy them and send to unknown random address no one has private key for.

We have been doing it since day one.....unintentionally....

I was reading somewhere that there is at least 2 mil of coins that is unreachable if not more. Sent to addresses with errors, under pile of garbage on an old laptop disk etc. All burned coins that will never be accessible. If you look at it that way, taking in account all permanently lost private keys, we are regurarly burning coins.