[perching_aix]

> mixed with basic rules about subject-verb agreement (...) [that] I would expect as a basic requirement for passing high school English

I reckon this is just a poorly picked example on your end, because the guide explicitly states the following about that:

> There are two forms of agreement: subject-verb agreement and pronoun-antecedent agreement. Subject-verb agreement is pretty rudimentary, and is not discussed here.

Regardless, sometimes (oftentimes?) technical documents are written by people who are not actually technical writers. A good number of those will also have a native language other than English. And in a lot of high schools, passing the English class is really not a very high bar, especially when failing people en masse is not really an option. You can only coerce people to learn a language so well.

[starkparker]

Yep. About half of the content in my workplace's style guide wouldn't need to be in it if those rules weren't repeatedly broken by borderline-illiterate software engineers who are brilliant with code, probably, but write in fragments, end sentences in commas, and pluralize words with 's. Getting consistent SVA in their writing might as well be two pay grades above them.

[Cthulhu_]

You'd think / hope / expect editors and IDE's would put squiggly underline's under incorrect apostrophe'd plural's, but ala's.

I always assumed it was mainly a thing with Dutch people who have English as a second language, given that using 's for plural's is common, also in words shared with English like baby's or ski's, but it seems to be an issue with English speaker's too.

[perching_aix]

There's one area where I also struggle with apostrophes and pluralization, that being acronyms which must be kept lowercase. Whenever I hit such a situation, I usually just reword the entire sentence just to avoid it.