The 3rd stage of the annual John Van Caneghem Tournament (2007).

It seems there was also a mention of a bug with exchanging army units/artifacts in the altar for experience, or something about selling artifacts at an inflated price.

So, what exactly is it? This should be in the rules. Because I personally use the altar. Regarding selling artifacts, I only know that there's a bug if you sell them from your backpack. But if you sell them directly from your hero, everything will be fine. That is, you need to sell them in parts: sell everything from your hero, exit, equip the next batch of artifacts from your backpack, go back to the artifact trading, and sell everything from your hero again, and so on. Then you won't be able to exploit the bug to inflate the price of artifacts.