The fact that “query” and “ask” are synonyms in English does not make the patterns the same.

The key design goal in this thread was to create a pure functional core, which you can “ask” things of. That pattern is useful on both the command and query side of a CQRS system, and a different thing from splitting up mutating and reading operations as CQRS proposes

Maybe I misunderstand you though. Say you have a CQRS system that reads and writes to a database. Are you proposing the query side be implemented in pure side-effect-free functional code? How should the pure code make the network calls to the database?

Then why the weird assertion that "command" code can only do things and not validate input?

That is not something that’s necessary for all CQRS systems, but maybe is something you’ve heard for the subset that people call “Event Sourcing”? There it’s a design goal that the system only records events that are occurring, so there’s no domain level validation that can be done on the command path - the user pressed the button whether we like it or not, so to speak. Whether the event has the intended effect is worked out after the event is recorded.

But there’s nothing in the more general idea of “separate reads from writes” that mandates “no validation on writes”

Commands can validate their input in CQS. What they don't do, in strict CQS, is return values. They can set state which can then be queried after execution which can let you retrieve an updated result or check to see if an error occurred during execution or whatever.