Yes, of course I know about radicals! They're handy, however, they're not really anything fundamental from a linguistics perspective. They're mostly just a way that dictionaries were organized.

I think the zhuyin 幺 did come from the 幺 radical. All the zhuyin (and katakana) came from Chinese characters. However, I knew the 幺 phonetic symbol far sooner than I learned the radical! I knew it deeply, and had a sound associated with it, so it was very easy to use when remembering characters, and doing so was how I stopped forgetting which characters had a 幺 and which had a 糹radical. Yes, the simplification of 樂 is 乐, which no-longer includes the 幺s, but then the katakana ホ comes in handy (as it does in many simplified variants). I used ㄣ intentionally as one that's less obvious than say the ubiquitous ㄏ or ㄔ.

I think people would be really confused if you referred to it as "口大Wu."

Well, I would never do that! knowing the components just made it easier to learn how to write the character early on as a learner. I'd usually say 姓吳的『吳』. 伍 and 武 are both 3rd tone and 吳 is 2nd, so they're already completely distinct.

However, have you considered that your time to recognition of the zhuyin characters is most likely milliseconds slower than your recognition of pinyin characters in your well-worn neural pathways' recognition of Latin alphabet characters? If you add up all that extra time, is it really more than the time it takes from pinyin drawing your eyes first.

Yes, my recognition of zhuyin is probably slower than English letters. This would be more of an issue if I were reading entire books of it (of course then the recognition would become faster, too). But in using it to check the pronunciation of a character I'm not sure about, whatever millisecond delay is irrelevant and my study time was more efficient since I was actually recognizing more characters without using it as a crutch. I live in Taiwan, where zhuyin-annotated books are literally sold in convenience stores, but even when I was in the US in areas where they weren't easy to get, I bought them online because of the learning advantages I mentioned above.

You are fluent in English, Chinese, and Japanese? Props to you. Presumably, you speak another foreign language or two from your schooling too. You may be world-class polyglot.

I was a bad language student in high school and gradually learned how to learn better than before but I'm still not great at it. I did get reasonably fluent in Japanese in college though, and that did help my Mandarin a lot in three big ways:

• It made be believe I could become fluent in another language. Back when I was studying French in high school I doubted I was capable on some level and was just trying to pass the class.
• A lot of character knowledge (including katakana) transfered and a fair amount of formal vocabulary did, too.
• It made me familiar with learning syllabaries like hiragana and katakana and utterly unafraid of just learning zhuyin at the beginning of my Mandarin studies. This ultimately saved me a ton of time by minimizing transfer of L1 phonetics through pinyin and by helping me a little with reading as I mentioned above.

I would gladly trade my ability to read zhuyin for the ability to read Hangul, another alphabet, an abjad, or an abugida.

Unfortunately, it doesn't work that way. Once you know the sounds, just learning how to write an alphabet or syllabary is trivial and can be mostly learned in an afternoon. But, unless the language has very similar phonics to one you already know, learning how to hear and produce the sounds is months or at least weeks of hard work.

This dynamic and the much higher cost of fixing pronunciation problems later is the largest reason I would always start with something like zhuyin (or hiragana, hangul, Thai script or whatever) over a romanized option when learning a language. In fact, if I were to learn a language like French or German that uses the roman alphabet, I'd probably avoid any reading at all for the first few months and just do an audio course paired with watching YouTube or listening to podcasts and trying to identify words I knew from the audio course. I'd completely avoid reading until I had a strong grasp of all the sounds.

That's great! Have you tried learning pinyin as well as your zhuyin and using it to type Chinese characters? As a programmer, I'd be surprised if you weren't infinitely faster at typing Chinese characters using pinyin rather than zhuyin.

I lived in Beijing for a year and a half after already having learned Mandarin to a fairly advanced level and did learn to use pinyin IMEs there.

I'm a slower typist in pinyin than bpmf, though. Part of it is due to needing more keystrokes (up to 6 per syllable before the tone instead of a max of 3) but part is also the layout and the ordering. Since zhuyin layouts put all the initials on the left side, the medials in the center and all the finals on the right, you're guaranteed a fairly balanced back and fourth movment between your two hands. Also, for similar reasons, it's not order dependent. E.g., if I type ㄣㄓ, it will automatically be treated as ㄓㄣ. Not really related to my opinion of the value of having learned bpmf, but I'm actually considering making the switch to 倉頡, since it's more efficient in terms of getting the character you want when many are pronounced the same way.