@Paul Hanslow Thank you, I think it's probably a bug in Fontbakery, I have the above-mentioned unicode assigned to these marks and the same naming convention.
That does not sound like a likely Fontbakery bug. I suggest filing an issue to find out which it is: if it’s a Fontbakery bug, you are doing a favor to the project; if there is something wrong with your font that you are missing, then that would be good to know. https://github.com/fonttools/fontbakery/issues
How or with what program are you compiling your fonts, and do the mentioned glyphs in the compiled fonts in fact have those unicodes?
The fontbakery report about unreachable glyphs highlights glyphs that a) don't have a unicode and b) are not in any feature substitutions, so are in fact "unreachable" for the user. That said, it sounds a lot more likely something in the compilation/font editor/post production is interfering in an unexpected way.
Comments
brevebelowcomb is U+032E
dieresisbelowcomb is U+0324
macronbelowcomb is U+0331
https://github.com/fonttools/fontbakery/issues