[stan_rogers]

Hwæm, actually, if you really feel a need to attach yourself to obsolete words. Language changes, and the dropping of whom should not bother you anymore than does here having entirely supplanted hither or the near absence of whence in everyday conversation.

[asark]

Garner's advice, to paraphrase—his entry on who/whom is, unsurprisingly, long—amounts to generally understanding and following the rules, but using whichever reads or sounds better if rule-following results in awkwardness, as it certainly sometimes does (he has examples). In this case I'd judge that either works, though the more formal-register the writing the more this use of "who" would stand out.

This being a headline in the Economist—and considering that, apparently, at least some found this use of "who" distracting, while "whom" would have been at least as easy to parse and probably wouldn't have bothered anyone—it's probably fair to call it a small error.

Garner also notes that predictions that "whom" is on its way out are, at this point, part of a long tradition, and do seem to capture the trend but do not yet describe current standard usage outside the fairly informal or colloquial. IOW for the best hope of communicating well at higher-formality registers, especially in writing, do continue (mostly) following the standard rules, in this case, avoiding it only when "correct" use is distracting or strange to a modern reader.

[enriquto]

In that case using the correct word would render the title unambiguous and comprehensible to everybody. As it is written I read it as "who was responsible for the act known as the Maya Sacrifice?". As a non-native English speaker who learnt the language in a rather formal way, interpreting the word "sacrifice" as a verb is ungrammatical to me.

[brianush1]

In this case, it would be "Who did the Mayan Sacrifice?" instead of "Who did the Maya sacrifice?" The lowercase "s" indicates it is not part of a proper noun, and "Maya" is a Native American group, and must be suffixed with an "n" to act as an adjective.

[mkl]

I think "sacrifice" is used as a verb at least as frequently as a noun. To me it's unambiguously a verb here as "Maya" is a noun ("Mayan" is the adjective).

[DanBC]

Anybody using English[1] will benefit from a good dictionary. All dictionaries show both noun and verb usage.

https://www.etymonline.com/word/Sacrifice

[1] I do mean anybody: people with or without English as a first language.

[qwsxyh]

As a native speaker, sacrifice is a verb.

[enriquto]

It can be a noun or a verb, depending on the context [0]. In this sentence it seems to be a noun, which is qualified by the adjective "mayan", written simply as a noun in apposition "Maya". If "sacrifice" is a verb, the sentence has no object, thus it is ungrammatical, because "who" cannot be the object, only the subject. Or so I was told when learning this damn language!

[0] https://en.m.wiktionary.org/wiki/sacrifice

[selimthegrim]

Hitherto is certainly used more often than heretofore or hereto (also hither and yon(der))