As Ian and Ryan already blogged, the Fedora Design Team is evaluating new branding fonts: Comfortaa for headings and either Cantarell or Droid Sans for body text.
Part of this test is language coverage, so I tried the weak point I know in support for Romanian language, the letters ș and ț (very few fonts support them, even for Liberation it took years to get them) and not to my surprise, both Comfortaa and Cantarell failed. Knowing from the Open Font Library what a great guy Dave Crossland, the Cantarell's author, is, I wrote to him, telling about those missing glyphs.
He not only replied fast, with a promise to improve the fonts and a preview of the patch (the 'regular' version of the font), he also gave me extensive advice about font editing (I expressed my lack of confidence in my font editing and hinting knowledge), including a screenshot, so I think I will share the knowledge:
FontForge screenshot by Dave Crossland
What I did was to open the kcommaaccent glyph (U+0137) and drag a guide down to -122 and copy the comma glyph shape. Then open the combining glyph U+0326 and paste it in, making it center-aligned on the origin (so the metrics are both -169). Then select the 4 accent glyphs you list, and at the element menu, Build, Build accented glyph.
...and make sure they are vertically aligned with the guide I just made, and "by eye" check they are horizontally aligned with the bulk of the black of the letter. See screenshot attached."
Thanks Dave, you are awesome! - that's an "upstream" pleasant to work with.