When woman as the vocabulary came up, I’m a bit fumed that the website registered my typing as “おんあ”, despite my intentions being “おんな”. Thing is, I remember exactly what the vocab was, and a simple typing conversion oversight shouldn’t be the reason that it shoots down from late Guru/Master back down to Apprentice.
Can the website at least give some form of warning for this specific kind of thing much like how it asks for an on-yomi reading when you’re giving it the kun-yomi?
This isn’t unique to WK, it’s just how Japanese IMEs work (at least by default). So if you’re typing Japanese in any other context you’ll need to double-tap the ん anyway. It’s good practice.
(Also, I’d recommend installing the Ignore script if you’re using a browser (https://greasyfork.org/en/scripts/9867-wanikani-override) to override pure typos like this.)
I think it’s a comparable case to mixing on’yomi and kun’yomi readings, so a warning is still fine. Some people might genuinely be wrong, but it’s far less likely than a typo.
The onyomi/kunyomi thing isn’t a mistake by the user. There aren’t any default “typo warnings” for readings.
All someone will achieve by overriding this type of mistake is getting in the habit of using a Japanese IME incorrectly. It’s better to learn how to type properly.
I make other more weird typing mistakes sometimes when I absolutely knew the answer and was trying to type it, usually when I’m going too fast an not paying attention this happens. In the long run you’ll have that one burned before you ever reach level 60. If it was already guru’d I think you don’t have to worry about either. It’s easy enough to learn not to make that mistake again.
I have made the same mistake… few times on fact, but after the initial shock I have been trying to better myself to check my answer before hitting the enter key.
This isn’t true- you’ll still learn, it just will be a little slower, but a lot less frustrating. I only make the ん mistake once in a blue moon now, and I’ve been overriding it pretty much my entire time here- it was the reason I installed the script in the first place.
Part of learning is figuring out what to prioritize for sanity’s sake. This is something that has fairly large benefits, at least early on, and very marginal drawbacks. At least in my experience.
No matter how long you’ve been typing in Japanese, you’ll still sometimes nyo your n’yo. Besides, overriding a ん mistake doesn’t type the word in correctly for you - you still need to type it again, and thus you still have to learn how to use the IME. And the frustration saved from not being set back by dumb typos can be immense.
If Tofugu/WaniKani had sufficient developer resources, a warning for this and other common mistakes would be very good to add to the beginning levels. It’d be advantageous for them to ease new users into the learning process.
That said, there are enough workarounds that I don’t think this is going to be a priority, so we’ll continue to see threads like this. 
I wonder how such a feature might even work… I suppose you could check for every word written with ‘nn_’ and if the answer for such a word is written ‘ん_’ … Can’t be too hard…
But that’s still a little cheating. It’s a wrong writing and shouldn’t be tolerated by the system. Of course, I would totally ignore such a mistake with the double check script myself. But they really don’t happen that much, you get used to it in no time at all.