Is assert(false) ignored in release mode?

If compiling in release mode includes defining NDEBUG, then yes.

See assert (CRT)

IIRC, assert(x) is a macro that evaluates to nothing when NDEBUG is defined, which is the standard for Release builds in Visual Studio.

The assert macro (at least it is typically a macro) is usually defined to no-op in release code. It will only trigger in debug code. Having said that. I have worked at places which defined their own assert macro, and it triggered in both debug and release mode.

I was taught to use asserts for condition which can "never" be false, such as the pre-conditions for a function.