Codes only work when they are only known and used between people that already know and trust each other. There is no point in using a code to communicate something with someone you don't know, because you don't know them. It's really that simple. In the scenario where the other person understands the code, there are two possible outcomes: (1) they understood the code, don't like you, now, and you might as well have just openly told them that you are zoo, and (2) they understood the code, are also zoo, or sympathetic, and you still might as well have openly told them, for all the difference it made. Codes that are not actually kept secret between *only* you and people you have trusted the code with, are absolutely worthless, and they were never meant to be used to figure out who you can trust. That's a completely backwards way of using them. This is also why, in real life applications, once a code is broken, or leaked, it is absolutely hazardous to keep using it, unless you're only using it in the capacity of deceiving interlopers, from that point forward. And, any code shared here can be considered leaked from conception, because you don't know who you're talking to here, anyway. It wouldn't be a matter of antis, or feds, catching on "eventually". You'd have to assume they caught on instantly.
I'm not trying to make fun, or dogpile, just trying to summarize a breakdown of why secret codes can't be used to communicate between perfect strangers.