Manny people mistakenly recognise Bopomofo as katakana. I use bopomofo and get this reaction a lot, it just have to mention its actually bopomofo/zhuyin and then they know what it is.

This is not true. If you need to type on your phone, everyone needs to know that the mainland used the Wubi input method, which is Katakana, and now uses Pinyin typing. Taiwan has always used the original Katakana input method. Pinyin typing was invented later.