Well, since the original thread has been somewhat derailed already, I might as well throw my opinion onto the pile.
I don’t remember if I originally used mnemonics that much. I probably did, come to think of it. Coming from Oregairu, it was easy to remember 「人」. The mnemonic is two people leaning on each other, but in the written form, you can clearly tell that one person is leaning on the other far more than the other - and no matter what, someone always gets the short stick. This is always what comes of cooperation.
It was incredibly difficult to forget that when I first came across it in the anime, and it’s still the character I’m most intimately familiar with at this stage, four years later. The best part was that I didn’t even have to try to remember it. If the mnemonic was just “it’s two people leaning on each other”, I probably wouldn’t have recalled it as easily - but because the protagonist turned it into a major plot point, it’s a very strong mnemonic.
That’s my problem with WaniKani’s mnemonic’s, I suppose. Some of them are crazy and weird, which helps them stand out in your memory more, but they’re still just isolated sentence-long stories that didn’t affect me emotionally or really make me think.
I recently tried coming up for a temporary mnemonic for this word: 編む (to knit). Since there are already a ton of Kanji that use the idea of ‘women’ as a mnemonic (e.g. 姦 (rape) is the three women [guy] raped, 安 (peace/relief) is “women feel at ease under a roof”, 家内 (word for “wife”) is “inside house”, 嫁 (bride) is a woman just about to move into a house, 奥さん (someone else’s wife) is a woman who is deep inside someone else’s interior and 姉 (older sister) is a woman with a dagger), so I thought of a woman knitting under a door. It was so easy to remember because I had taken note (though had not actually used) all the other mnemonics involving women.
So they can be useful - I just don’t like WaniKani’s mnemonics too much, and I never thought using mnemonics helped me to distinguish between lookalike Kanji all that much. They can also get pretty convoluted when a Kanji character isn’t really suited for the mnemonics, and consequently become really hard to remember, if you know what I mean. Using mnemonics feels that way for me often.