Mnemonics have always caused some trouble, either because they’re the best for some people or the worst for others. Some love political correctness and others love how daring they can be. Some mnemonics make a lot of sense, but others just make you go “Whaa…?”.
Here’s a solution:
Allow people to thumbs up/down mnemonics during lessons/reviews. This way, you (the Wanikani team) will actually know how your users feel about them and better able to adjust your work towards that. You’ll be able to know which mnemonics need adjustment and which don’t. It makes your work a lot more focused.
Let the community help you.