So this doesn't use any new javascript, right? HTML only? 
It does use a bit of JavaScript, but only what's emitted in the onclick attribute on the <button> element (and that JS is self-contained).I would only be worried about my bot scraping posts with this new button and not being able to actually see the content because it requires some js embed on the bitcointalk page.
Nice catch. Factoring both you and Loyce into my thinking was part of the reason I settled on the approach that I did. That is, this feature should continue to work correctly in the context of HTML post scraping, without any special handling. (The only difference, and I find it to be a sensible one, will be in how the "Show" button itself is styled: on the forum proper it'll have the non-rounded and blue-tinted appearance that I think makes it look at-home in the context of a Bitcointalk post or PM, but on Ninjastic it'll just look like an unstyled button, I think, which would appear natural to me in the context of a post archive.)