Sorry, SPA may be the wrong term, I just meant that a Discourse thread kind of behaves like a single page app in the sense that pagination is happening dynamically…
Yes, I guess it does make sense. I tried searching for some text on page 3, Google brought me to page 3, so that seems good. Wrong spot on the page, but seems probably as close as we can get in this situation.
So in retrospect, I guess having the pagination canonicals does make sense on longer threads, but if you look at the best practices for SEO, the guidance is to not allow Google to index paginated content with identical title and meta description. I guess the solution here is to change the title and meta on successive pages. See:
Source: SEO-Friendly Pagination: A Complete Best Practices Guide