#1682 (comment) resolved that:

RESOLVED: treat invalid counter styles the way we treat invalid font faces

The spec change log says:

@counter-style rules that are invalid due to missing descriptors just fail to create a counter style; they’re otherwise still valid rules.

I understand these resolutions as: if a @counter-style rule has wrong descriptors, it should still be parsed into a valid rule and appear in the OM; it only fails to create a counter style and hence do not affect any counter.

However, the current spec text makes the entire @counter-style rule invalid in some cases:

If the system is cyclic, the symbols descriptor must contain at least one counter symbol, or else the @counter-style rule is invalid.

If the system is fixed, the symbols descriptor must contain at least one counter symbol, or else the @counter-style rule is invalid.

If the system is symbolic, the symbols descriptor must contain at least one counter symbol, or else the @counter-style rule is invalid.

If the system is alphabetic, the symbols descriptor must contain at least two counter symbols, or else the @counter-style rule is invalid.

If the system is numeric, the symbols descriptor must contain at least two counter symbols, or else the @counter-style rule is invalid.

If the system is additive, the additive-symbols descriptor must contain at least one additive tuple, or else the @counter-style rule is invalid.

If a @counter-style uses the extends system, it must not contain a symbols or additive-symbols descriptor, or else the @counter-style rule is invalid.

Should they be revised into not defining a counter style?