A card the target ignores

The target’s silence, made loud

A card the target reads and then ignores is written exactly as stated, and the compile says so: the deck carries a target.keyword_ignored warning naming the card, printed once through ps.PetroScriptWarning:

import warnings

with warnings.catch_warnings():
    warnings.simplefilter("ignore", ps.PetroScriptWarning)
    quiet = ps.compile(flood.replace(numerics=ps.Numerics(stack_depth=25)))
assert [issue.code for issue in quiet.issues] == ["target.keyword_ignored"]
assert "NSTACK" in quiet.files["FLOOD.DATA"]   # written as stated

PetroScript writes what you stated and tells you what the target will do with it.