WaniKani has a fuzzy spell-checker, which results in similar words being accepted if they are only a few letters different.
If the wrong word is easy to confuse with the correct word, the @mods can add the wrong word as a blacklisted word to the item. That means you can’t answer with that word even though it’s close in spelling.
You can make that kind of request anywhere, but some people have started using this thread for that purpose. Feel free to do whatever you prefer.