What burns out the tweeters is the amount of power it is getting after the onset of clipping. the RMS power goes from the .707 of peak and becomes 100% with 100% clipping which equates to 2X power of that original power rating. And, tweeters are very low power capable to begin with. I seriously doubt that a 1/2 watt of square wave would burn out the tweeter.
Since there is a reversal in a sine wave from pos to neg, it is not really DC, just a longer duty cycle, much longer and still AC.
And, the amount of those odd harmonics also increase from the onset to full clipping as you indicated.
Would having the Mute ON from your amp with the Master Volume level cranked to max, and then release the Mute button to OFF, cause a little distraction to the tweeters? With a Heavy Metal CD playing of course.
Yep, that's what I also thought, after getting nailed for $400 for my two tweeters.
* I muted my amp for a small break (pee time), while that CD was still playing. Then my very nice brother was looking for a bit of back ground music, instead of totally muted. So, without knowing that the Mute button was on (on my remote), he simply raised the Master Volume to try gettting some misic (music), but he just kept crank it up. Then, I came back from the bathroom, and he ask me, hey Bob, how do you get misic from that thing? Well, I said, you have to get the Mute button OFF... You guess the rest...

Talk about a sudden death dose of adrenaline going to our ears, our brains, our hearts, and my tweeters.
Any of you had a similar experience?
* Oh, by the way, that amp was delivering normally about 300 watts per channel into my
4-ohm speakers. But the way we did it, was a very sudden death. I don't really care how many watts or what, I just know that it's a no no.