Why do some people have the verified checkmark?

You can add the Twitter-style verification icon to your profile by adding :verified: to the end of your display name, but anyone can do this, and proves authenticity just as much as adding a smiley face or any other emoji to your display name, i.e. it's fun but it doesn't prove anything at all.

To help people have confidence that you are who you say you are, you can add one or more URLs to your Infosec.Exchange profile and then verify control of that URL.