Theme 1 – Ultra‑small, auditable kernel
“Metamath's Python verifier - its trusted kernel - is just 700 lines of Python short” – 7373737373
Theme 2 – Logic isn’t baked in; many foundations are interchangeable
“In Metamath the axioms are not built‑in… you can use intuitionistic logic, New Foundations, HOL, or design your own” – dwheeler
Theme 3 – Users favour familiar tools and resist forcing a single prover on everyone
“I find it really strange that people who don't use Lean don't just get on and use the alternatives rather than trying to get everyone who is using Lean to use something else.” – seanhunter