> When people buy a domain for their blog, it’s a clear sign they intend to stick around.

If you go through comments on some popular post from the golden age of blogging (~2011?), where people's names would link to their sites, the free wordpress.com or whatever blogspot blogs are up much more often than the custom domain ones.

Funnily enough, often the last post on the free blog will be the announcement of switching to a domain, now inactive.