This comment got me confused about the status of BIP66 (Thanks jnewbery for explaining) The comment was added in: #3843 But in #5713 strict DER encoding was enforced in consensus, and is now it's buried and enforced by the height of the block here: https://github.com/bitcoin/bitcoin/blob/4af01b37d40246cd1fdb54719855927e36a36b46/src/validation.cpp#L1889
P.S. This is also quite confusing: https://github.com/bitcoin/bitcoin/blob/4af01b37d40246cd1fdb54719855927e36a36b46/src/validation.cpp#L1560-L1563 But seems to be intentional: https://github.com/bitcoin/bitcoin/blob/4af01b37d40246cd1fdb54719855927e36a36b46/src/validation.cpp#L1510-L1511