John Vertical wrote:
> Doubtlessly many of you have noticed that the "IPA Extensions" block in 
> Unicode has several characters which do not appear in the official IPA. 
> These symbols are apparently (mostly) from older versions. So, this begs 
> the question: what did they stand for? Here's what I've deduced so far; 
> can anyone confirm?
> *Iota and closed omega (ɩ ɷ): [I_x U_x]. Tho I've also seen 
> some systems position closed omega as an _unrounded_ [U].

Archaic equivalents of [I] and [U]. They appeared in older IPA charts.

> *Esh and ezh with loops (ʆ ʓ): [S_j Z_j].

Palatalized [S] and [Z]. I've seen them in older descriptions of the IPA.

> *Reversed t and k (ʇ ʞ): central alveolar and velar clicks, 
> respectively.

I don't recall exactly how these were described in the IPA charts; 
Pullum and Ladusaw says that turned t is a dental click. A velar click 
is, of course, unlikely in a human language, although that is supposedly 
what turned k was for.

> *Stretched c (ʗ): and old symbol for the palatal click.

Pullum & Ladusaw's comment is that this is "Illustrated by the click 
that q represents in the Zulu orthography, which is generally referred 
to as 'palatal' in the literature, but has also been called 'retroflex,' 
especially in earlier work".

> *"r with long leg" (ɼ): a retroflex trill (or was it a fricative 
> trill?)

Fricative trill, as in Czech.

> *"Squat reversed esh" and "turned r with fiskhook" (ʅ ɿ): I 
> have heard that these are "retroflex vowel" and "alveolar vowel", but 
> that makes little sense.

These are used for the sounds in Mandarin Chinese written as "i" in 
pinyin, in words such as "shi" and "si". Not officially part of the IPA. 
They sound like prolonged versions of [z`] and [z], but without friction.

> But about the "inverted glottal stop" (ʖ), "closed epsilon" 
> (ʚ) and the turned h's with left hook (ʮ) or with left hook 
> and a right tail (ʯ) I have no idea at all; nor about the whole of 
> "Phonetic Extensions" block with all the letters like "capital ou" or 
> "sideways m" or "ain".

The "inverted glottal stop" was a lateral click (x in Zulu or Xhosa). I 
believe I've seen the turned h's with hooks on a web page on Chinese 
dialects. I don't know specifically which sounds they represent.