Selection bias. The nature of Reddit and its past as a liberal free speech zone lends (lended?) itself to particular traits. Reddit’s average user is some combination of the following:

• male
• in a STEM job or training/educated for STEM work
• grew up middle-class
• downwardly mobile
• has ADHD or autism

Altogether this does actually mean IQ probably trends a bit higher on average. That doesn’t mean shit for the quality of your arguments if you don’t critically examine your beliefs though, and anyone sprouting American media talking points is not examining anything.