And I suppose neither of us answered your question as to whether we had experience with a square forge. Nothing like a goober weigh-in with opinions without any knowledge of what you actually asked for!
The answer for me is "No".
But I have seen them in use and as I stated, they do indeed work. What I have noticed is they tend to have a hot spot which is much more pronounced than in a round forge. As you know, ideally on a round forge the burner is inserted at an angle and thus, the flame swirls around, more efficiently heating the whole forge. Square forges/burners that I've seen, can't do that and the burners are typically pointed right at the bottom, producing the hot spot. (Or Two hot spots if it is a two burner) That may work fine for forging, or heat treating. But with Damascus welding, I't think it would be important to have more even heating.
And they may work fine for Damascus. Like I said, I'm a goober answering your question without any hands-on knowledge.
