The point is, AI detectors aren't that accurate so don't fully rely on it.
You've oversimplified it. Because of these types of grammar/capitalization errors, I would never assume this was an AI-generated post:
I believe you should take a look at bitcoin. As you can see, many bitcoiners have demonstrated that they have made significant profits from the currency. It all depends on whether you are willing to take the risk. Many investors choose Bitcoin because of its rapid growth, but if you'd rather something more secure and low-risk, consider investing in gold. Here's the idea: To decide which of the two investments you should make, start with a small sum of money. For instance, you could invest the same amount in gold and bitcoin, then watch to see which one is more profitable and able to quickly recoup your initial investment.
Just about every AI detector gives false positives at some point, so its a good idea to check multiple detectors. Some are better than others.
For the text in question, here are the results from all the detectors:
Sapling.ai - 100% fake (occasionally produces false positives)
Hivemoderation (the most reliable detector) - 4.7% likely to contain AI Generated Text
Copyleaks - AI content detected (this one no longer provides a % so I'm not sure it should be used anymore)
Writer.com - 28% human-generated content
Writefull.com - 65% likely this comes from GPT-3, GPT-4 or ChatGPT (not a high enough score, threshold for reporting based on a detector should be 70%)
So yes, based on the results of Hivemoderation and Writer.com, this post could be reported as AI-generated. Except for one thing which you mentioned earlier: the post was written before ChatGPT was released.
The other way to combat the false detection problem is to only submit reports if 3 or more of the author's posts are highly likely to be written by AI based on detector results. If its a one-off thing, it probably shouldn't be reported (unless its clearly spam).