I looked into this more. Reddit (created by Steve Huffman and Alexis Ohanian) merged with Infogami (created by Aaron Schwartz). There are people calling Aaron Schwartz one of the founders, but that doesn't seem entirely accurate.
In the early fall of 2005, he worked with his fellow co-founders of another nascent Y-Combinator firm, Reddit, to rewrite its Lisp codebase using Python and web.py.
This is more than just "merging his company into Reddit".
Just because one outside source merges with another, doesn't mean you're a founder of the source that you've absorbed to. That'd be like saying Microsoft and Apple merged, so Steve Jobs is a founder of Microsoft. It doesn't work like that. He'd still be considered a founder of Apple.
That’s not the best analogy. A better one would be Tesla, which started in 2001, incorporated in 2003, but didn’t meet Elon Musk until 2004. He’s listed as a co-founder. https://www.tesla.com/elon-musk
Yeah, I have noticed this too. Nobody really ever mentioned him as a founder of reddit before a few years ago, and now it’s like some legend of internet lore. He was famous for different things and never called a founder of reddit from what I recall.