My toxic trait is using fixed width fonts whenever possible but especially for email because if the official software *forces* me to use HTML email then I’m gonna make it look correct for everyone.
(anyone else remember the HTML email wars? oh how I long to be upset about just that once again.)
@futurebird html email is a huge security and privacy problem. Its widespread acceptance enabled widespread use of privacy-invading emails that track whether your computer fetched images or other remote things referred to in the html, as well as many other privacy invading techniques. It enabled the rise of the adtech industry, which is currently backing the nazi administration in the USA.