EDIT: I misunderstood OP, I thought the comment was saying there was zero proof of Huffman's ability to tamper in the first place. Agreed there's no way to prove he can't do this anymore.
Mind quoting the passage that describes the measures in place? I just read the entire article and absolutely zero proof is provided that Huffman can no longer edit things.
It mentions Spezgiving, followed by Huffman's apology, and then moves onto banning subreddits, to the meeting about banning subreddits, and ends at /r/Place and the worry it'd be nothing but swastikas. Absolutely nowhere is anything described about the measures in place to prevent Huffman - or anyone else at Reddit for that matter - from editing posts.
There's precisely zero proof of this.