The only "example" I can find there is a reference to the Great Depression, which is only considered an example of a deflationary spiral because there exist no better examples. The Great Depression was cause by a number of events in concert, most of which are actually bad political and international trade policies. The example of the Panic of 1920, and the fact that it's nearly identical to the first two years of the Great Depression, is evidence enough that a deflationary spiral is, at most, a minor contributing factor to the depth of the Great Depression. I say that it's a false theory.
That said, what counter examples would you give of prosperous societies with permanent deflation?
Easy peasy, since I get to choose the time frames. Any society that has ever existed upon a gold standard, prior to that same society's move towards currency debasement. You're getting your cause and effect wrong, The Roman Empire didn't collapse because they used a deflationary currency (gold, silver, salt, nails) they debased that same deflationary currency because they were in the process of multi-generational collapse. Money is simply a tool.