@BeAware@wjmaggos Quote reply, where you link to their post and call it out. Screenshot their post to do the same, etc. You don't always have to directly reply to a person to call them out if they're spreading misinformation. Now that is more so warning others about that person.
If you want to correct that person directly, provided they're not acting in total bad faith, you should still be able to @ or message them.