Mixed reality company Magic Leap just released its not-quite-a-development-kit headset, called the Magic Leap One. Responses have been mixed. It’s an ambitious and functional product, but one that’s made significant compromises without delivering a uniquely powerful experience. But Oculus co-founder Palmer Luckey has delivered one of the harshest assessments so far, calling it “a tragedy in the classical sense” and prompting Magic Leap’s CEO to respond with an extended Avatar: The Last Airbender analogy.

Oculus Rift inventor Luckey bought a Magic Leap One, and in a blog post, he argues that bad design decisions make it barely a viable product. He calls the headset interface “basically an Android Wear watch menu that floats in front of you,” and while software can be fixed, he argues that Magic Leap’s magnetic controller tracking is hopelessly compromised. “It is less of a functional developer kit and more of a flashy hype vehicle that almost nobody can actually use in a meaningful way,” Luckey writes.

A lot of Luckey’s post seems like potentially fair criticism. I’ve only used the Magic Leap One once, but I can vouch for the interface comparison. And Luckey isn’t dissing a competitor here; he left Facebook-owned Oculus to found a border surveillance tech startup last year.

But it’s not just a dispassionate technical assessment. The piece is fueled by frustration with Magic Leap’s hype campaign, which Luckey complains “sucked all the air out of the room” for other companies. Luckey used a quirk of Magic Leap’s purchasing process to estimate that around 3,000 headsets have been sold, and he argues that many of those people are interested enthusiasts, not actual creators.

Magic Leap co-founder and CEO Rony Abovitz, a known lover of oblique pop culture subtweets, escalated the conversation into an extremely nerdy beef:

While this isn’t as harsh as the time Abovitz suggested Microsoft’s HoloLens might give you permanent neurological damage, it’s an extension of his long-standing public disdain for competing headsets. In fact, Abovitz keeps a 19th century stereoscope in his office to illustrate how fire-bending — I mean, stereoscopic 3D — is ancient and allegedly obsolete. (The “banished” reference likely refers to Luckey’s less-than-amicable final days at Oculus.)

Soon after his Avatar tweetstorm, Abovitz called for peace and unity because “there are enough rifts in our society,” which may or may not be an even subtler dig at Luckey’s signature creation.

Luckey is simply voicing a more pointed version of some common Magic Leap criticism in his post, and the Magic Leap One is a specialized product whose buyers probably won’t be deterred by one negative review. But his conclusion — that Magic Leap’s technology makes it a virtual non-starter, not just a rough first step — is damning.