How ethical is it to use bugs like the Phoenix bug and the clone bug? I heard that the Chinese don't even hesitate and actively use them when completing maps. Is this true?
Some maps are specifically designed with this in mind. I can recall "Where the Beauty Lies," where the author specifically describes this bug and explains how to complete the map with a hero and legions of archers. Otherwise, it's impossible to complete it.
In other cases, this technique is very rarely used. In my opinion, it's more of a bug, and I wouldn't use it. Although, right now, when completing "Legend of the Shanghai," with 30,000 Grand Elves (with a possible berserk), this technique would be helpful.