[css-syntax] Adding an at-rule to a list of rules comes with an unexpected caveat #1839

5.4.1. Consume a list of rules

The instruction to consume an at-rule currently states:

<at-keyword-token>
Reconsume the current input token. Consume an at-rule. If anything is returned, append it to the list of rules.

The caveat "if anything is returned" is unexpected since 5.4.2. Consume an at-rule always returns an at-rule, and never gives instruction to "return nothing", even upon a parse error. Since this caveat does not appear elsewhere when consuming an at-rule, I suspect it was included accidentally.