I went through 169 published blog posts and 30 pages to correct the URL for one of my sticker artists because they moved to a new carrd.co URL.
Attempting to MySQL REPLACE() my way to success did not work, presumably because of Automattic's Jetpack fucking with things.
I did not fix all the broken Twitter embeds caused by people jettisoning that website. I'm not sure I'll have the energy to, ever.