I've RPed villains in FF since 2.0, and I typically do it publicly. I think it adds to the fun, both for me as the villain having to pay attention to things like who's around, and for the other people around me. It adds flavor. I do expect anything I do or say publicly to be used against me, but this is where it gets into odd territory.
If I want my character to swing a sword at someone, I get to post that they're swinging the sword. I don't get to post what the result is, however. That's up to the other person. That's very well accepted.
But does that only apply to physical fights? Or should it apply to other things? Cops 'n' robbers, off the script, is basically the same as that RP sword fight. It needs to play out - in my opinion - similarly. The spy can use the information they gathered against my character, but it has to happen in that same manner. And this, in my opinion, is why the answer to the question "is communication key?" is yes. Absolutely yes.
At the end of the day, the ideal for RP is that everyone involved in a RP is doing it to make the collective story better. That's why I RP my characters' villainy in public. Likewise, if my character is spying, I'll make some sort of post that at least can indicate that my character is actively there (as opposed to standing still as if I were afk). It makes for a better story. At the same time, we've all probably run into someone who tries to RP to "win". It's one of the reasons why lots of people RP fights resolved with /random - it avoids that possibility in a combat RP. Silent omniscience in a character - whether it's a spy who literally can't be distinguished from an afk person or a villain who decides "no one can spy on me ever" - raises red flags in the same way as a character who always dodges a blow in a fight RP does. OOC communication can mitigate those red flags.
If I want my character to swing a sword at someone, I get to post that they're swinging the sword. I don't get to post what the result is, however. That's up to the other person. That's very well accepted.
But does that only apply to physical fights? Or should it apply to other things? Cops 'n' robbers, off the script, is basically the same as that RP sword fight. It needs to play out - in my opinion - similarly. The spy can use the information they gathered against my character, but it has to happen in that same manner. And this, in my opinion, is why the answer to the question "is communication key?" is yes. Absolutely yes.
At the end of the day, the ideal for RP is that everyone involved in a RP is doing it to make the collective story better. That's why I RP my characters' villainy in public. Likewise, if my character is spying, I'll make some sort of post that at least can indicate that my character is actively there (as opposed to standing still as if I were afk). It makes for a better story. At the same time, we've all probably run into someone who tries to RP to "win". It's one of the reasons why lots of people RP fights resolved with /random - it avoids that possibility in a combat RP. Silent omniscience in a character - whether it's a spy who literally can't be distinguished from an afk person or a villain who decides "no one can spy on me ever" - raises red flags in the same way as a character who always dodges a blow in a fight RP does. OOC communication can mitigate those red flags.