Assuming that there also exists a rule regarding no hidden text, there isn't really a way to "hide" an encrypted string of your role, much less to repeat it multiple times with nobody noticing. With Adel's strategy, it's likely that town forces everyone to post it in their first or one of their first posts, likely with nothing else (similar to what happens in games with lie detectors, where people get forced to make a plain single-post statement like "I am aligned with the Town"). Already we can see that, even if you have some crazy crumbing strategy strung out over 30 posts, there's nothing to say that you didn't do the same thing for twelve other roles somewhere else and perhaps with some other method in your posts. In that regard, there's no guarantee that that is the singular role that you were intending to hide. In comparison, encrypting your role and posting it as your first post
Furthermore, crumbing strategies such as pop-culture media references, typos, random capital letters and deliberate word choice can (in some cases) plausibly have been thought of after the fact. If I'm the kind of person who normally pops into the thread and might talk a little about some medical drama I was watching or something similar, my later trying to claim that this is a Doctor crumb is made weaker by the fact that I might have done that even if I wasn't intending to claim doctor. There's an element of doubt. You might counter this by saying that some references could be so clear cut or otherwise out of character as to
Even further, crumbing strategies have some element of counterplay, which I don't believe is the case for encryption. If I made the medical drama crumb that I mentioned earlier, it might not be too much of a stretch for scum to see that and think that I'm crumbing and kill me. Even if I'm the kind of person who stretches a crumb out over multiple posts, it's still theoretically possible to counter that as scum. You might argue that that's unreasonable, but I would say that if you become known for doing weird crumbs like that then it immediately becomes less effective, as scum can know to look out for that. Nobody might normally go over the first letter or last letter of every post, but they might if they know that that's how you like to hide things. Even if you're not
Any sort of counterplay to an encryption strategy like Adel's would have to come from the social side rather than the "linguistic analysis" side, I guess I'll call it. That is, trying to convince people not to do it in the first place. And, considering that, I would say that the only objections one
So if we have something where:
1) The only reason not to do it would be on grounds of poor sportsmanship, and
2) It would be done every game if not banned
Those already seem like fairly decent grounds for banning something, not to even mention other considerations such as moving things away from the game of mafia itself, and that most things in mafia that don't come from the moderator shouldn't be able to be provable like things can be with cryptography (correct me if I'm overlooking something else provable).
Honestly, if we're discussing strange rules that seem inconsistent or don't seem to have much justification, I would say that the common rule against provable randomness makes much less sense.