Fair question. The answer is that they didn’t bother hiding it. They literally posted in a whole bunch of Iranian subReddits and only Iranian subReddits. On this thread they were claiming they were British. Literally the first post of that kind, completely different to everything they had posted previously.

The clincher was that they deleted their account as soon as I pointed they were Iranian.

I’m going to guess they bought a Reddit account from someone without looking at the past history on the account.