To be honest, its more likely they're concerned with grammar than spelling. They don't want broken English, the administrators probably just want grammatically-correct sentences.
Since its a Visual Novel, players will be doing a lot of reading rather and language and communication is everything in word-based games likes PAL. Those small errors in language can cause problems and even cause confusion for readers who are trying to understand their responses.
While not exactly the same example, this year's release of Mass Effect: Andromeda is a great example of miscommunication of dialogue choices and communicating what the author is suggesting you might say.
With the loss of the Paragon/Renegade system from the classic trilogy, people have been complaining about how bad the dialogue choices can be, or how confusing and indifferent each dialogue choice is compared to one another. There is no real way for you to play a "bad" or a "good" Ryder like they did with "good/bad" - "Paragon/Renegade" Shepard.
Having better grammar improves the gaming experience overall.
"The difference between Reality and Fiction? Fiction has to make sense." - Tom Clancy (1947-2013)