I think probably Disco Elysium is more about dualities and mirrors, exits and returns, and sides of coins than it is about triples.
But this did not stop me from losing my mind about Lely's jaw scar/the Law Jaw/what's his nuts that Rene saved in the war. I had some THEORIES.
And again I think the mirror image intended is probably Harry|Klaasje, but consider the ways in which Harry|Lely|Klaasje are the same person served up 3 ways. 3 tools set to different applications and how each is warped in its own fashion.
"It's just like that... As if you opened the internal doors to the night and admired the movement, without understanding what was happening! Then, you have to close them to be able to feel all the wonders that could happen in your life in the morning!"