You answered your question early on in your original post, super tweeters are utterly worthless. Let your boiling blood cool off, and ignore those who talk about super tweeters. Whether you're for or against them, it isn't worth getting steamed up about them.
The post you are responding to is a few years old. I think there is a place for super tweeters, but they are more about achieving technical goals than practical ones. A lot of dome tweeters will start beaming above 10kHz, but what if you wanted your speaker to maintain a wide dispersion above 10kHz? a 1/2" super tweeter can do that. Or, what if you wanted to use a heavy-duty tweeter with high power-handling, but it only played up to say 10 kHz before running into problems. Cross it over to a super tweeter. There isn't much real content above 10 kHz, but there is some, and you can hear it, so you might as well address it. I don't think there is any point in having concern for performance above 20 kHz, but supertweeters can have use in frequency bands below that range.
