I think if the rule is equal for all just make in the way I can't post one word, if the moderator is there to contribute as a human being he has to understand the context before automatically applying the rule. If not he is just another bot here.
The problem is not the number of words, it's about what it brings to the forum. And regardless of how you personally feel about it, the answer in most cases is that short replies like "thanks", "great", "good project sir" just bump the thread for hundreds of users, add it to watchlists, etc, and don't really carry any useful content. There are different environments for chatting, like Discord or Telegram, where garbage just flows off the screen and no one ever reads it again. This forum is not like that, or at least we're trying to make it not like that, despite the best efforts of millennials to twitterize it.