Letters with comma below are similar but distinct from cedilla for proper
romanian support. Unicode does not have these letters with grave accent
(which is like a comma except above) so this is the obvious and only
available mnemonic.
!A ǂ # Alveolar; !- looks alike, != even more so but already occupied
!B ʘ # Bilabial
!R ‼ # Retroflex (or Repeated); !! looks alike but occupied
+# grave (or similar)
+R! Ȑ # no R-grave; double down
+r! ȑ
+S! Ș # no S-grave; comma in use for cedilla, so misusing grave seems only fair
+s! ș
+T! Ț # no T-grave; like S!
+t! ț
# subscripts
as ₐ