You just acknowledged that there are transactions with >83 bytes in the blockchain added before v30. But then you immediately contradict yourself by saying, “and now in addition large OP_RETURNs are possible”. Clearly, they were already possible, if there were already “around 15” added before v30 (I think there is a lot more, and my query is still running). So how do you reconcile this contradiction in your mind, while still believing that the change to the default settings in the v30 client makes a difference? I can help you out: it doesn’t. Changing the default settings in a client does not affect consensus rules. All valid transactions can and will be added to the blockchain. Client settings are not consensus rules. What is your preference, spam in a prunable field, like OP_RETURN, or spam in permanent ones, such as UTXOs? As BitMex research showed by storing images in private keys, everything in Bitcoin is data, so it will always be vulnerable to abuse.

BitMEX Blog

Bitcoin OP_RETURN & Image Storage: Spam Debate

Abstract: We look again at the OP_Return policy limit issue and the related topic of storing images in the blockchain. The argument is not going a...