This reminds me of my all time favourite lost redditor that asked for a Adobe Acrobat alternative on r/freeuse (which is not about free software but very nsfw). They were extremely helpful though.
/trees only happened because there was a power tripping mod that was banning everyone from /weed, and the arborists hadn't shown up yet cause the Digg/Slashdot migrations hadn't happened yet, and when they did show up they decided to be snarky about it, lol.
There was apparently a significant population of German car mechanics on /r/BBW as well.
lost redditors was great fun, I remember that /r/Burial (about the musical artist) used to keep a running count of confused morticians that would wander in.