From @yeli-renrong:
Are there examples from outside the Sichuan/Yunnan/Tibet area of the development of postocclusion, as in ɬ ɮ > ɬtʰ ɮd? Is this even diachronically correct, or is postocclusion here a retention after a development of e.g. *l.t- > ɬᵗ?
Examples of "suffricates" as an etymologically single segment aren't exactly common in general of course. At least Bulgarian / Old Church Slavonic *ť *ď > št žd and (some?) Ancient Greek *ď > †zd are diachronically clear cases. If Sino-Caucasianists are on to anything, Burushaski has t- : -lt- from earlier *tɬ. None of these, though, come from a fricative. So yes maybe suggestions of earlier *ɬ *ɮ are indeed simply incorrect and should be rather *lt- *ld- or *tl- *dl- or *tɬ- *dɮ-. The development of Written Tibetan zl- to some varieties' /ld-/ might then be simply routed as fortition to *dl (additionally via *zdl if wanted) plus metathesis. Per Hill (2011: 446) this metathesis has been already proposed long since by Simon in 1929. Or maybe that should be rather Proto-Tibetic *zl-, since this metathesis seems to precede WT!
Tangentially on the topic, Awngi has notably been described as having /s͡t ʃ͡t/, similar to affricates in occurring at syllable boundaries even word-internally. They also fail to be ever broken up by epenthetic [ɨ], but at least this argument is not followed consistently: other homorganic clusters like /mb/ or /rt/ are tolerated within a syllable too; moreover, both the "prestopped fricatives" and certain "tolerated clusters" trigger epenthesis of initial [ɨ]. There does not seem to be evidence for an earlier monophonemic origin. It looks to me that allowing minor complication in syllable structure (existence of some cases of -CC.C- not epenthesized to -CCɨC- or -CɨCC-) would be a better analysis than positing fairly exceptional contour consonants, which brings to my mind the weird Africanist style of analyses that sometimes suggest even clusters like /kɾ/ to be "single consonants".
For that matter, a strictly epenthetic nature of [ɨ] is not tenable for modern-day Awngi anyway: this analysis is originally due to Joswig, who however admits that it is (1) not followed by loanwords from Amharic, (2) not followed by the native noun [sɨsqi] 'sweat' (**[ɨssɨqi]), (3) bled by a proposed degemination of a variety of consonants. All these problems would seem to be solved by treating epenthesis of /ɨ/ as a historical sound change and not a synchronic process.
