"Best practice" for SEO is that you keep the URL and routinely update it. I have no idea if that's fully correct, but it's what we're basically told to do. Clearing out old comments or creating a new thread is something I'd like to do as well, but I don't have the power to do that short of creating a new URL for an article and redirecting, which potentially loses some "SEO juice" or something.
Back in the old days (pre-2015, say), the normal approach was to just make new articles, and leave all the old stuff in place. I liked that because it meant I didn't have to go look for old stuff to redirect, and all that information was available for historical reference. But times change, and various publications have apparently figured out that updating existing articles and redirecting ends up being better for Google rankings.
Yet another case of Google essentially dumbing down aspects of the Internet. Just like an SEO article like this will say "AMD vs. Intel" a hundred times to make sure Google really knows how invested we are in discussing AMD vs. Intel CPUs. It's pretty much a throwback to the early days of the Internet with meta keyword overloading, and it sucks for writing because you end up sounding like an imbecile. All hail Google, our search overlords!