The anagram was a huge push thanks to Nasu's history with this kind of naming, but what got me supporting David is Daybit for real was the bit on the final Bluebook scene where he muses about his hyperthymesia. The comment about how "everyone called me a genius" matches the first thing we hear about Daybit, and him explaining what hyperthymesia is by claiming he can remember his friends' smiles in vivid detail hits the exact same level of cheesiness Daybit reached when he claimed his friendship senses warned him that he needed to save Pepe.
There's also the also the connections between the alien, the void element, and Brishsan, but that's a pile of interconnected assumptions.