The issue is that there is no way to derive a distinct key from an npub. All tweaks are reversible by the server and so they can derive your nsec easily, so the electrum server would know your nsec (and that is why I compared it to Anigma). A list of candidate npubs’ tweaks can be subtracted and checked. Even asking an LLM would have found this issue. Cryptography is hard to get right and so unless you have a good reason, don’t roll your own schemes. If you do, do some research. Just make a new keypair.