The KeYmaera X developers are incredibly thankful for the helpful feedback on its early versions from their power users.
If you have a question about KeYmaera X, either ask on the KeYmaera X mailing list or directly ask the right person based on the primary responsibilities listed below.
Nathan Fulton: Bellerophon tactic framework, tactic parser, tactic extraction, lexer and declarations parser, Mathematica interface, HyDRA web API
Stefan Mitsch: user interface, tactic library, tactic tracing, lemma mechanism, command line, HyDRA web API, task scheduler, Mathematica interface, SMT interface
André Platzer: prover core, parser+printer, unification-based calculus tactics, forward tactics
Brandon Bohrer: proof tree model interface, proof database, security, tactic data for UI
Ran Ji: SMT interface (Z3, Polya), code generation