Some alphabets capitalize proper nouns, others capitalize all nouns.
Does ipa notation ever get capitalized to match their written counterparts?
I would assume not, as it might be sending mixed messages - especially if they could represent different IPA letters. I don't have a definitive answer though.
The official chart showing the International Phonetic Alphabet is downloadable from the IPA website. IPA letters are not defined in cased pairs. Most of them look like lowercase letters (and I believe are treated as lowercase letters in Unicode encoding; I don't know if there are any exceptions to that). Some look like small caps; these are just separate letters, representing separate sounds. (Usually the sound is similar in some regard to the source letter, but there is no single rule connecting the sound of an IPA letter that looks like a Latin alphabet small-caps letter to the sound of an IPA letter that looks like the "corresponding" Latin alphabet lowercase letter.)
Obviously, the IPA letters a, b, c... z, which are identical to letters of the familar Latin alphabet, have upper-case equivalents A, B, C... Z in the context of the larger set of Latin alphabet characters, but these upper-case equivalents are not formally defined as part of the IPA, and there is no common informal use for them in phonetic transcriptions that I know of.
In phonological transcriptions, full-sized capital letters of the Latin alphabet may be used in a way Typhon mentioned in a comment below:
I have seen upper case used to denote archiphonemes in broad transcriptions. I'm not sure if it's standard practice. – Typhon
I would say this still isn't exactly "capitalization" because the capital letters don't correspond to a single lowercase IPA letter, but to a set of them (e.g., N might be used as a symbol representing the neutralization of both /n/ and /m/).
Also, a transcription with archiphonemes is fairly definitely not phonetic (I don't mean to say that there is a clear line between phonetic and phonemic transcriptions, just that I think most people agree that no matter how blurry the line is, archiphonems are on the phonemic side, and maybe even beyond it i.e. on a "third" level).
The practical orthographies of some languages contain letters taken from the IPA (or from other similar phonetic transcription systems), and in this context, capitalized/uppercase letters often may occur. But these are not official IPA, just similar but distinct scripts. There are even some upper-case equivalents to certain letters of the IPA outside of the 26 basic Latin ones: while these uppercase forms are not part of the IPA, they are used in some alphabets like the "Africa Alphabet" (which has Ʃ as the upper-case form of ʃ, Ʒ as the uppercase form of ʒ, Ŋ as the uppercase form of ŋ, and some others).
In the case of the glottal stop letter <ʔ>, there is some variation. It is used as a case-invariant letter in the orthographies of some languages, but there is also a pair of derived characters that are used as a cased equivalent in the orthographies of some other languages: uppercase <Ɂ> and lowercase <ɂ>.
You can see more examples at the Wikipedia article Case variants of IPA letters
No, you can't capitalise IPA characters, because there are enough IPA characters that look like upper case letters that it would be very confusing: ʙ, ɢ, ʜ, ɪ, ʟ, ɴ, and ʀ are all distinct IPA characters and are not the same sounds as b, g, h, i, l, n, and r.
IPA transcriptions transcribe sounds or phonemes. Even when in a broad transcription a symbol represents a phoneme, it is in some sense referring to a group of possible sounds, which can contrast with another group of possible sounds to differentiate meaning. IPA transcriptions make no allowances for the orthography or written conventions of language apart from in three specific ways:
Most transcription systems allow for white space between words. This is just to make the transcription easier to read. It is not for any kind of punctuation reason.
When a group of scholars decide upon a convention for representing the phonemes of a particular language in language-specific, phonemic transcriptions, they may sometimes choose one symbol over another because it more closely resembles the orthography. So, whereas Southern Standard British English /e/ is in between [e] and [ɛ], most authorities use /e/ as opposed to /ɛ/ to represent the phoneme because this is how the phoneme is most often 'represented' in the orthography. This it is felt, will make life easier for learners of English, who will have to use these transcriptions in dictionaries and language learning materials.
When used in written essays about phonetics or phonology, lists of phones or phonemes are often separated within their brackets by commas. The comma does not feature as an IPA diacritic and so serves to show that we are talking about a list of discrete phones or phonemes and not a string of sound or a string of phonemes. So people tend to write [p, t, k] or /p, t, k/, for example, as opposed to /p/, /t/, /k/ and so on.
This, however, is as far as it goes. We do not allow for punctuation marks or capitalisation and so forth in phonemic or phonetic transcriptions. Phones and phonemes do not have capital or small case realisations! Several other problems would arise if we did. First of all many symbols used in punctuation have a distinct specific meaning when used in IPA transcription. To illustrate, the exclamation mark, < ! >, represents an alveolar click; an apostrophe < ’ > after a consonant makes it ejective. Most importantly here, the IPA system actually uses small caps capitals to represent specific types of phone. So [ʙ,ɢ, ʜ, ɪ, ʟ, ɴ] and [ʀ] are completely different and distinct sounds from [b, g, h, i, l, n] and [r]. If you use a < B > to represent a [b], you will actually be indicating a voiced bilabial trill—in other words a bilabial raspberry—instead of a plosive.
IPA transcriptions match sounds not their written counterparts!
No, IPA is used to describe only how words are pronounced, which is independent of how the words would be written in any specific writing system. Capitalization doesn't have any meaning in spoken language.
You are never supposed to capitalise letters, though small capitals are sometimes used (e. g. the bilabial trill is represented as /ʙ/ and the uvular trill is /ʀ/). It would be both confusing and irrelevant to capitalize letters, considering especially the confusion that would occur when presented with vowels such as /ɑ/ and /a/, both of which have the capital counterpart ⟨A⟩, or /œ/ with its counterpart ⟨Œ⟩, which is reminiscent of the open front rounded vowel /ɶ/.
This might help: https://en.wikipedia.org/wiki/Case_variants_of_IPA_letters
There've been cases (no pun intended) where I find myself in need of IPA in upper case.
NEVER capitalise IPA. In IPA, the only form of capitalisation is with the small capitals like /ɪ/, /ɢ/, /ɴ/, /ʀ/, /ʏ/, /ʙ/, /ʜ/, and /ʟ/
