tl;dr: Pandoc creator John MacFarlane recounts the 20-year evolution of the document converter from a 3000-line Haskell project (started as an excuse to learn the language) into a tool supporting 51 input and 76 output formats, with contributions from 600+ people. Key milestones include the CommonMark spec, Lua filter support, citation processing, WASM compilation, and the recent split into modular packages. MacFarlane credits Haskell's type system and purity for making long-term maintenance feasible, but speculates that LLMs may eventually reduce the need for deterministic converters like pandoc.