Comment 1 for bug 670758

This bug is quite broad and so quite hard to deal with, of course the desire of the big (support for everything ever) is laudable, but to actual make that happen we'll have to break it down and tackle it in much smaller bite-size chunks.

From an end-users' point of view, the desire will be to add the glyphs that a particular script/language requires, but from an implementors' viewpoint, Dalton Maag have a preference for ensuring that whole Unicode blocks are included in one go in order to ensure harmony across the typeface.

I'll go through the codepoints that you've specifically raised and the blocks that they are in. Currently the UFF includes Latin A+B not some of the other blocks:

  Ɛ (U+0190), Latin Extended B: done
  ɔ, ɛ (U+0254, U+025B), IPA Extensions
  x̀..xͯ (U+0300..U+036F), Combining Diacritical Marks
  x᷄..x᷇ (U+1DC4..U+1DC7), Combining Diacritical Marks Supplemental

Gaining coverage by way of doing full-blocks means:

  IPA Extensions: 95 glyphs, ~45 straight composites of existing Latin/Greek
  Combining Diacritical Marks: 111 glyphs, ~100 straight composites, placement work
  Combining Diacritical Marks Supplemental: 43 glyphs

For the latter, 36 codepoints are already grabbed by the Ubuntu Font Family (drawn as the unknown numbered square glyph), but do not appear to have a glyph associated. See the coverage map from Unicode for these:

  http://unicode.org/charts/PDF/U1DC0.pdf