Are there are IPA symbols which are the subject of some controversy? For example, I suppose there are some who would like to have a unitary"tS" t-esh sound as a unitary phoneme... but I bet there are loads of other examples. I'd really like to learn about any ongoing/resolved discussions about IPA symbols... Thanks!
Oh yes, very much so! The IPA is constantly changing and expanding, and existing symbols are moved, repurposed, and deleted. Many linguists still use the "Americanist" system, for instance, which prefers diacritics to new symbols (/š/ instead of /ʃ/) and single symbols (like /č/) for affricates.
To give a few other examples:
- Some people like affricates being written as two separate symbols, but others prefer to give them their own symbols (since they're often phonemic). So as a compromise there used to be ligature letters like /ʧ/ and /ʦ/.
- Until 1895, /q/ was used for the voiced velar fricative. It was then replaced with "g with a loop" (as opposed to loopless /ɡ/), and then with "g with a bar", before finally becoming the modern gamma /ɣ/.
- Until 1989, clicks were written with Latin-like letters /ʇ ʗ ʖ/ rather than /ǀ ǃ ǁ/. This was a subject of significant debate, which affected some languages' orthographies.
- By analogy, /ʞ/ was proposed for a velar click. In 1970 the IPA changed their minds and said that a velar click was impossible, and removed the symbol. But now some linguists suggest that it's possible and found in some languages; the debate is ongoing.
For more examples, see Wikipedia's summary.