Well, in WK they call 頁 “geoduck”, so 日正頁=> “sun, correct, geoduck” is not complete randomness (they even appear in correct stroke order in the mnemonic sentence)
This work was already in the back of my head from… Somewhere. Fortunately, I could just ignore the mnemonic on this one.
The WK mnemonic for this worked fine for me, but even if it didn’t, I’m not sure what more you could really do for the word ‘topic’ when the radicals you have to work with are sun, correct, and geoduck. 
They could have used the kanji Page instead of the radical Geoduck (which let’s be honest, is a hit or miss one) tie it all together, something like how you have to write the topic of a lecture correctly on a page and the topic is sun. This sentence has a better narrative. WaniKanis mnemonic fail to tie the idea of a lecture with any of the radicals, so there’s no real association here.
There are so many good associations between topic, sun, page and correct, even just the fact that the sun is up in the sky the topic is on the top part of the page and that is correct.
In some cases using what the kanji has to offer is way better than trying to invent the wheel.
Thank you! For using the word “association.”
A mnemonic is supposed to tie what you are memorizing TO something else, like triggering something you already know that helps memorize the new thing.
This “mnemonic” for TOPIC, is just a self-contained, random image that doesn’t relate to anything else outside of itself.
You are saying topic is the missing link itself, but there is still nothing that LINKS them. So the radicals contained in the kanji could be ANYTHING and it wouldn’t affect the “mnemonic.”
car + tree + water. That is the TOPIC of today’s lecture.
ice + parent + star. That is the TOPIC of today’s lecture.
wind + horse + small. That is the TOPIC of today’s lecture.
Or the MEANING could be ANYTHING and it wouldn’t affect the “mnemonic.”
sun + correct + geoduck. That is what I drew on my BACKPACK.
sun + correct + geoduck. That is the PASSWORD for my computer.
sun + correct + geoduck. That is the METHOD the detective used.
And I’m not even getting into what does it mean to “use the sun”…
The missing link is 題 itself.
Basically you have “題 = topic”, but reworded as “日、正、頁 = topic”.
you need to already have an image of those kanji associated with the words sun, correct, geoduc, and be able to instantly “see” those components in 題.
If you don’t like to remember a silly English sentence, you can try using Japanese readings
Eg: 題 => 日正頁 => ひ・ただし・ぺージ for example.
This would be inconsistent with how the rest of the system works. ‘Page’ is associated with the Kanji 頁, not the Radical 頁, which is ‘Geoduck’ in WK.
For 題, we do not have the full kanji 頁 like we might see in something like 頁岩, but the radical 頁, which is just a component of the single kanji 題.
Remaining consistent with how Radicals are used as building blocks to create mnemonics for Kanji meanings is more important (for content provided by WK) than how much sense it makes, as freely mixing and matching using radical and kanji meanings in mnemonics used for other Kanji would create even more confusion.
You could argue against using ‘Geoduck’ as the meaning for the radical in the first place (I personally like ‘geoduck’ but that’s just me), but that’s a completely separate argument.
Sometimes there just isn’t a great way to make a strong association between the Radicals, Kanji, Vocab, Meanings, and Readings, and in these cases they need to work with what they have.
In this particular case, what they have to work with to make a mnemonic is
題 : 日 正 頁 = sun, correct, geoduck = ‘topic’
with which there isn’t that much that can be done (I feel ‘topic’ would be a difficult case with almost any combination of radicals).
You have to write the topic of a lecture correctly on a page and the topic is sun
IMO, using the kanji meaning ‘page’ here isn’t making a stronger association between the radials and the kanji meaning of ‘topic’ as it is still relying on the idea of a ‘lecture’ to get to ‘topic.’
Of course there is absolutely nothing wrong with using the mix of radical/kanji meanings in this way to help you get to ‘lecture’ if that helps you get to ‘topic.’ If that is what works for you then you should ABSOLUTELY use that. There’s absolutely nothing wrong with coming up with your own mnemonics! But that just isn’t the methodology that creators at WK can/should be using for the content they provide.
Everyone will have cases where they have unique things that help them remember something better than the provided ones, and for these cases I highly recommend using the ‘Note’ section for a given Radical, Kanji, Vocab entry to record the mnemonic that worked for you so you can refer back to it later if needed.
I agree with this most of the time, but sometimes an exception to the rule (in this case consistency while using radicals) yields better results, since the surprise of something being inconsistent can serve the mnemonic emotional hook. It means that those inconsistencies should be few and far between of course, otherwise it’s indeed a recipe for chaos.
Personally, I treat WK as a starting point, a suggestion. If 70% of the mnemonics WK provides work for me, I’m happy.
WK is just an aid after all, it can do some of the work for me, but at the end of the day I’m the one who does the learning so doing that extra work where it’s needed is just part of the process.
A geoduck wakes up and sees it is not the correct sun in the sky and says, “Whaaa?”
“WA” is the sound of the TOPIC particle.
There I have just LINKED these radicals to “TOPIC.”
A geoduck walks out on a sunny day and has to apply the correct TOPICal cream to avoid a sunburn.
There I have just LINKED these radicals to “TOPIC.”
The TOPIC of the song, “Who Loves the Sun” by the Velvet Underground is heartbreak. A geoduck burrowed underground because it was heartbroken that his geoduck wife did something that wasn’t correct. (She slept with his cousin on a bed with velvet sheets, which is a TOPIC he doesn’t like to think about).
There I have just LINKED these radicals to “TOPIC” with an admittedly obscure reference, but WaniKani does that a lot, which I don’t mind - I actually enjoy learning about them as long as there is some LINK.
(Like Tetsuo: The Iron Man or the Bosozoku bike gangs).
Now here is the BEST mnemonic I can think of:
A geoduck says the word “sun” and an owl says, “That is the correct TOPIC!”
JK - That “mnemonic” triggers no associations to the word TOPIC in one’s memory so it is extremely weak just like WaniKani’s.
Now maybe if there were a famous story about an owl (perhaps a friend of Christopher Robin deep in the Hundred Acre Woods) who is a conceited, know-it-all. Piglet asks owl what the heck is a geoduck, and owl has never heard of those, but he has to appear correct about EVERY TOPIC so he explains in his pompous way that “geode-ducks” are million-year-old rocks with crystals inside that are shaped like a duck and when you break them open and hold them up to the sun, the crystals shimmer and sparkle. But if you want one, you have to pick them out of the ground.
Again I say - Whoever came up with this “mnemonic” really phoned that one in.
This is the first mnemonic I’ve seen mentioned in this thread that actually fits the general formula and I think it’s actually really good (don’t think I’ll need it at this point but I’m copying it into my notes just in case).
Must say this is an ingenious solution! I think it would be if you’d suggest it to WK mods perhaps they’ll use it? Only if you feel like it of course.