The following is an excerpt from an article about spelling mistakes:
Can you spot the mistakes? Building signs which get standard English phrases wrong; posters and other material featuring misspellings, mangled grammar, eccentric constellations of English words and outright mistakes ...
The highlighted part of the phrase does not sit right with me. Is this wording (a) grammatically allowed and (b) does it sound natural to a native English speaker?
Yes, it's grammatically fine, if semantically distinct.
For how it sounds to native speakers, a Corpus of Contemporary American English search for "GET * wrong" led me to the phrase "got it wrong," and I found several results where the entity isn't a person:
we think the United States had got it wrong (Fox News Sunday, Interview with H.R. McMaster, December 3, 2017).
the media has got it wrong (Fox News, January 17, 2017)
the polls got it wrong (The Boston Globe, "Pundits, politicians failed to detect depth of Trump's support," November 9, 2016)
Abigail R. Montcrieff, Reincarnating the " Major Questions " Exception to Chevron Deference as a Doctrine of Noninterference (Or Why Massachusetts v. EPA Got It Wrong), 60 Admin. L. Rev. 593 (2008).
That bill got it wrong. (Fox News, "Interview With Fred and Jeri Thompson," July 15, 2009)
Especially in the last three examples, inanimate objects get something wrong. In these instances, the actual people responsible are implied: pollsters got the polls wrong, the Supreme Court got Massachusetts v. EPA wrong, and legislators got the bill wrong. Why? Perhaps it is convenient to focus on the inanimate object, since the alleged error is most clear in the object itself. That compares favorably to your own example - the author may not even know who made the sign, but alleges the sign is wrong. It's a small step to then say, "The building signs get standard English phrases wrong," as if the sign commits the error each time it is read.
There are no grammatical issues with an inanimate object serving as a subject here. In this case, the usage is colloquial, which is why it tends to appear in verbal transcripts or in asides within titles. If you want to label the usage rhetorically, it's a kind of anthropomorphism, which gives an inanimate object human qualities.
Expanding on my comment as I didn't quite get what you found wrong with it.
The phrase does seem to imply that the mistake was made by the building sign. However as you say inanimate objects do very little voluntarily, so that can't be true. If the sign itself didn't make the mistake then the mistake must be elsewhere – probably with whoever specified it or who made it.
If we expand to its full meaning then we'd arrive at something like:
Building signs where whoever made it or specified it got standard English phrases wrong.
But this is quite a mouthful, and doesn't really exhaust all the possible reasons that the wording on the signs might be wrong. In this context, though, we don't care who made the mistake or why it was made, we just want to spot the mistakes. It's probably more correct to say Building signs which have standard... but using which instead doesn't mask the actual meaning.
Building signs which get standard English phrases wrong;
Since it is followed by a semicolon, it should be an independent phrase (with a subject and a verb). There is no verb. It might be reworded as:
There are building signs that get standard English phrases wrong:
Here, the colon sets off the list that follows.
In my opinion, it sounds natural to an AmE speaker.
