This is my understanding but please correct me if some of my details are wrong:
- In 1946 the Japanese language underwent a reform and standardization process
- A subset of kanji (about 1850) were made official and others more or less obsoleted
- A smaller subset of kanji were simplified, the new forms becoming known as shinjitai and the previous forms as kyujitai
But some words which used characters made obsolete were respelled with similar looking characters, my favourite being:
"濠洲" (ごうしゅう, Gōshū), an ateji for "Australia" became "豪州"
- Does this replacement of characters have a name? They are not shinjitai since they already existed and they are not in shinjitai tables.
- Does this only happen with ateji or also with regular words?
- Does it only happen when the replacement characters have a same reading as the replaced characters?
- If not, does this add to the confusion of which readings apply to which characters?